The concept of a “chemical-free lifestyle” is absurd

From Tim Minchin’s introduction to his brilliant song, “The Fence.”

Chemophobia is alive and well. It is difficult to get on the internet without celebrities, friends, and family members bombarding you with concerns about chemicals in your food, hygiene products, vaccines, etc. Indeed, being anti-chemical seems to be extremely fashionable at the moment, and you will often hear people talk about living a “chemical-free lifestyle” or trying to “avoid chemicals.” The problem is, of course, that everything is made of chemicals. Literally all matter is made of chemicals, and if you truly lived a chemical-free lifestyle, you would only live for a matter of minutes, after which you would die from a lack of oxygen.

I’ve written about this topic before, and I don’t want to spend this entire post belaboring the point, because it is a fundamental and basic fact of science that I shouldn’t have to explain. You are a biochemical machine that ingests and inhales chemicals (food, water, and air) and uses chemical processes to release energy from those chemicals so that the energy can be used to power your body. Everything you do is the result of chemical reactions. I could spend a long time explaining all of that in more detail, but for this post I want to focus on why it is important to understand that everything is made of chemicals and why we shouldn’t let people like the Food Babe get away with making claims like, “There is just no acceptable level of any chemical to ingest, ever.”

You see, when I point out the ridiculousness of trying to avoid chemicals, many people accuse me of pedantry and say that people who say that they are trying to avoid chemicals do know that everything is made of chemicals, they are just using the word chemical to mean “toxic” chemicals, or sometimes, “unnatural” or “synthetic” chemicals. Beyond the fact that they are distorting the definition of “chemical” to suit their own fears and biases, that response is very problematic, and I want to talk about why.

First, I’m not convinced that everyone is actually aware that everything is made of chemicals. Remember, the Food Babe was also concerned that airplane cabins didn’t have 100% oxygen, and she claimed that saying the words “Hitler” or “Satan” to water would change the water’s physical structure. So, at times we are clearly dealing with an extremely low level of scientific literacy and understanding.

Having said that, I can accept that most people probably do know that everything is made of chemicals, which brings me to my second and most important point. Using the word, “chemical” as shorthand for a “toxic” or “unnatural” or “dangerous” chemical creates a false dichotomy and fundamentally misrepresents chemistry. It ignores basic facts about chemistry, and in so doing, it dangerously misleads the public.

Let’s start with this notion of toxicity and assume that when someone says something like, “There is just no acceptable level of any chemical to ingest, ever” they really mean, “There is just no acceptable level of any toxic chemical to ingest, ever.” That statement is still fundamentally wrong, because the most basic concept of toxicology is that the dose makes the poison. There is no such thing as a “toxic” chemical; there are only toxic doses. Every chemical is toxic at a high enough dose and safe at a low enough dose. You can literally overdose on water if you drink too much of it in a short period of time. It is actually toxic to you at a high enough dose. Inversely, a few molecules of a chemical like cyanide won’t hurt you. Apple seeds contain cyanide, yet no one worries about accidentally ingesting one because the dose present in the seeds is far too small to be harmful to you. It’s not toxic at that dose. In other words, cyanide itself is not toxic to you as an organism. Rather, it becomes toxic at a high enough dose, just as water does.

As you can hopefully now see, even the concept of having a “[toxic] chemical-free lifestyle” is absurd, because all chemicals are toxic at a high enough dose. This concept proposes a simplistic false dichotomy between toxic chemicals and safe chemicals, while totally ignoring the fact that the dose is what makes something toxic. To be clear here, if you want to check the doses of chemicals present in your food, shampoo, etc., and also check the dose at which they become toxic to you, I have absolutely no problems with that, but that’s not what most people do. Rather, they view chemical toxicity as an entirely binary state. They view each chemical as either being toxic at any dose or safe at any dose, and they judge the safety of products merely by the presence or absence of a given chemical, rather than by looking at the dose. This simplistic view of toxicity is childish and dangerous.

Moving on, others use phrases like “chemical-free lifestyle” to mean a lifestyle that is free of “synthetic” or “unnatural” chemicals. This meaning is, however, even worse than the previous one. First, it once again assumes that chemicals can be placed into binary categories of “safe” or “not safe” without considering the dose. This is wrong. Both synthetic chemicals and natural chemicals have dose response curves. They are all toxic at high enough doses and safe at low enough doses.

This brings me to the second problem, namely, this argument is an appeal to nature fallacy. Nature is brutal and doesn’t give a crap about you. Nature will kill you in a million unpleasant ways, and the fact that something is “natural” tells you absolutely nothing about whether it is safe or beneficial. Remember earlier when we talked about cyanide? That’s a natural chemical. So is lead, aluminium, mercury, arsenic, formaldehyde, etc. Indeed, even if you lived in a pre-industrial society, you would naturally be exposed to most of these chemicals, and that would usually be fine, because they are all safe at low enough doses. The same thing is true when we talk about “synthetic” chemicals that scientists developed in laboratories. They are not inherently any more dangerous than a natural chemical. All chemicals are just combinations of atoms, and some of those combinations are only safe at very low doses while others are only dangerous at a very high doses, but all of them have a safe dose and a toxic dose. Where they originated is completely irrelevant.

As you can hopefully now see, statements about “chemical-free lifestyles” or “avoiding chemicals” aren’t wrong simply because everything is made of chemicals, but also because they represent a fundamental misunderstanding of chemistry and toxicology. These statements implicitly assume that some chemicals are always bad while others are always good, and that simply isn’t how chemistry works. The dose is what determines whether or not something is safe and chemophobia is irrational and misinformed. If someone tries to scare you about a chemical, ask them for the dose at which it is present in the item in question and the dose at which it becomes toxic. If they cannot answer both of those questions, then they either don’t know what they are talking about, or they are intentionally trying to mislead you.

Note for clarity: When I say that all matter is made of chemicals, I mean all matter at the atomic level and higher (obviously atoms themselves are made of subatomic particles).

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Acupuncture is just a placebo

acupuncture does not workAcupuncture is an extremely popular form of complementary alternative medicine (CAM) that has even worked its way into many “integrative” hospitals. It is also fiercely defended by its believers. Unfortunately, it is not well defended by actual evidence, so I want to talk about that evidence and explain why acupuncture is a placebo. As usual, my point here is not simply to talk about acupuncture, but also provide a lesson in how to critically read the scientific literature. Acupuncture has been studied literally thousands of times, and, as a result, the literature is a mess and it is very easy to cherry pick studies to fit whatever view you hold. Therefore, you need to critically assess the literature and apply appropriate logical and scientific tools to arrive at a good conclusion.


Acupuncture is based on pre-scientific mysticism. It is supposed to work via the manipulation of acupoints, but scientists have been unable to find evidence that acupoints actually exist (i.e., they are not physiologically distinguishable from other points on the body). Additionally, there is no known mechanism through which acupuncture could work. Nevertheless, thousands of tests have been conducted. Meta-analyses and systematic reviews of these tests are extremely inconsistent, with little agreement among them. Many analyses failed to find evidence that it is better than a placebo, while others found a significant difference. However, the positive results usually had very small effect sizes, suggesting that the results were not clinically significant and were likely statistical flukes. Further, these studies also documented a large placebo component to the treatments. Additionally, several studies have documented a positive bias in the literature, with higher quality studies tending to produce more negative results. This lack of mechanism, large number of negative results (especially from high quality studies), inconsistency among studies, and small effect sizes all indicate that acupuncture is nothing more than a placebo.

Purported benefits

What does acupuncture actually treat? According to its disciples, pretty much everything. According to the Center for Integrative Medicine it treats allergies, depression, dysentery, numerous forms of pain, stroke, nausea, morning sickness, headaches, labor difficulties, and multiple other conditions. They also say that it can probably treat acne, alcoholism, palsy, asthma, diabetes, infertility, herpes, schizophrenia, whooping cough, and a dizzying array of other ailments. Erectile dysfunction is, of course, also on the list, because no miracle cure would be complete without it (I wonder where the needles go for that one).

Whenever you see a list like this, huge red flags should go up. This type of list is one of the hallmarks of quack remedies (details here). It is simply not possible that a single treatment is going to cure everything from infectious disease to recovery from stroke. Now, you might try to get out of this by saying, “well, just because it doesn’t work on all of these doesn’t mean that it doesn’t work on any of them.” Technically, that is true, but how are you supposed to know which ones it works on, and why should you listen to the people promoting it when they are clearly trying to deceive you about at least some of its benefits? When someone says something like, “putting needles in your skin will cure your herpes” they have just lost all credibility, and you should not be getting medical advice or treatments from them. In other words, at the very least, these types of lists should make you very skeptical.

It is also worth mentioning that one of the problems with alternative medicine (including acupuncture) is that it tends to be poorly regulated, and practitioners get away with making outlandish claims that lack evidence to support them (something actual doctors can’t and don’t do; Ryan 2017).

Implausible mechanisms

Before we get to the literature itself, we need to lay some groundwork. Acupuncture is based on the pre-scientific notion that there is a life force (or energy) know as qi, and the correct flow and balance of this life force keeps you healthy. Acupuncture then “works” by inserting needles into “acupoints” along “meridians” of the body to cure diseases by correctly directing the flow and balance of qi. In other words, it’s magic. Any treatment that is based on the notion that diseases are caused by energy imbalances, blocked energy, etc. is pseudoscience, and should be rejected. You don’t have a “life force” and energy imbalances and blockages don’t make you sick. That’s pre-scientific malarkey.

Now you may be tempted to suggest that the people who developed the method “thousands” of years ago didn’t understand the mechanism and explained it with their pre-scientific superstitions, but the method does work, they were just wrong about the cause. That’s technically possible, but we’d need some pretty good evidence to conclude that it was true, and that’s where we quickly start running into problems. You see, meridians and acupuncture points aren’t real things (Ramey 2001). Their number and position changes based on who you talk to, and they don’t map to any reliable underlying physiological structure. Also, it is worth mentioning that acupuncture as we know it is probably not nearly as old as most people think.

Nevertheless, you can find many papers whose titles and abstracts seem to disagree with what I just said, but when you actually start looking into them, it quickly becomes clear that acupoints don’t exist. This is one of the fascinating things about the acupuncture literature. People seem to desperately want it to work, and the result is that there are hundreds of studies that spin fanciful tales without having that data to back them up.

Let me give you a few examples. Consider the paper “What is the acupoint? A preliminary review of acupoints” by Li et al. (2015). This paper acknowledges very early on that acupuncture points aren’t supported by evidence and aren’t distinguishable from other parts of the body.

“At present, there is no persuasive evidence for the existence of acupoints. For example, their location or number and the evidence from histological studies for acupoints are unconvincing.”

It sounds like we should be done at the point, right? But the authors continue, “This review focuses on the function of acupoints from different perspectives, which might explain what an acupoint.” [sic] In other words, “there is no evidence that these things are real, but we want them to be real, so we are going to go ahead and write an entire paper about them as if they are real.”

That’s not how science works, but there are tons of papers like that. Zhou and Benharash (2014) is another good example of this. Their paper was published in the Journal of Acupuncture and Meridian Studies, which, as you can imagine, is pretty heavily biased towards acupuncture (it’s a quack journal). Nevertheless, they stated, “These observations confirmed that there were no particular structures that were unique to acupoints.” This fact is reiterated numerous times in the paper. Yet despite this fact, they latch onto the observation that there are usually nerves near acupoints and spend the whole paper talking about hypothetical mechanisms as if they are established facts. It is true that you can usually find nerves near acupuncture points, but there are nerves just about everywhere in the body, so it’s not particularly interesting. If acupoints were real things that had medical relevance, then they should be distinct and physiologically identifiable, but they simply aren’t, and that’s a huge problem.

This brings me to my next major point. Despite thousands of studies being conducted on acupuncture, no one has been able to demonstrate a mechanism through which it works. Oh, there are tons of hypotheses, but no one has actually been able to convincingly demonstrate a mechanism, and that’s another problem. It’s a standard that we wouldn’t accept for pretty much any other form of treatment. Imagine that your doctor described a drug, and when you asked what the drug actually does, they said, “No one knows. Scientists have looked at it for years and can’t figure it out, but trust me, it totally works.” You’d probably be pretty skeptical about that drug.

Now, to be clear, having an established mechanism is not 100% necessary to demonstrate that something works. You could still do it with really convincing clinical trials, but, as I’ll explain in the next section, the level of evidence required is much higher.

Low prior probability

Prior probability is a very important concept in science that I have previously talked about at length. Briefly, it is the probability that a given result could be true given everything else that we know about the system in question. In other words, we already know a lot about the human body, chemistry, etc. As a result, before a given treatment is tested, we can have a pretty good idea of how likely it is that the treatment could actually work, and the more unlikely it is, the higher the evidence bar is going to be. This is very much in line with the saying that extraordinary claims require extraordinary evidence, and it is important because it is very easy to get spurious results from scientific tests. Therefore, you need to judge how confident you should be in those results. If a conclusion is implausible based on everything else we know, then we need really robust studies, large sample sizes, and large effect sizes before we can conclude that the result is real.

Now, let’s apply that to acupuncture. Here is the situation: it is based on pre-scientific superstition rather than medical knowledge, the acupoints that are fundamental to how it is supposed to work don’t actually exist, and there is no known mechanism through which it works. Indeed, if you just stop and think about it for a second, it is pretty implausible. How likely is it really that poking needles into the skin can relieve pain, cure infectious diseases, help with childbirth, treat gastrointestinal problems, etc.? It doesn’t make sense based on everything else that we know. Therefore, the prior probability is very, very low, which means that we need some extraordinary evidence to match these extraordinary claims.

As I said earlier, you could always acknowledge that most of these treatments are implausible (or even impossible), but still argue that some of them have a higher probability, and I will grant you that some are more plausible than others, particularly pain. It is conceivable to me that putting needles in the skin could have some form of neurological effect that might temporarily reduce pain, but it’s still not likely, and I still want some very strong evidence (especially given a lack of known mechanism).

What would it take to convince me?

I’m finally almost ready to start looking at the literature, but before I do that, I want to lay out exactly what it would take to convince me that acupuncture is actually an effective treatment. I find this to be a very helpful exercise that I encourage you all to undertake regularly.

First, I would need a very consistent body of evidence showing that it is better than a placebo. To be clear, when I say, “consistent” I don’t mean that every single study will agree. There will always be statistical noise and bad studies, but if it actually works, then it should be obvious when you look at the literature. There should be very wide-spread, obvious, and undeniable agreement among studies. Also, these studies need to be large and well controlled. Finally, it needs to have a large enough effect size that it is clear that it is a real effect, not a statistical fluke. In other words, it should be substantially better than a placebo (i.e., there should be an obvious clinical benefit). These criteria are very reasonable and appropriate, especially given the lack of mechanism and low prior probability.

The literature is a mess

The scientific literature testing acupuncture is a mess. There are always disagreeing studies in any field, and you can always find at least a few papers that argue for pretty much any position, but I have rarely seen such an incomprehensible mess. There are thousands of studies, a huge portion of which are terribly designed. Tons of them lack adequate controls, most of them are tiny (though there are exceptions), designs are extremely inconsistent with numerous methods being used and outcomes being measured, and biases and conflicts abound. Indeed, although there is a strong bias towards publishing positive results in general, it seems particularly dominant in acupuncture studies. As I said earlier, there are entire journals devoted to it. Plus, there are several acupuncture institutes that publish regularly, and it is well established studies from China (which accounts for much of the literature) are heavily biased and often involve inappropriate methods, inaccurate reporting, and biased reviews (Vickers et al. 1998; Wu et al. 2009; Ma et al. 2012; Wang et al. 2014). Indeed, studies from China (and other Asian countries) almost always report positive results, which is in stark contrast to studies from other countries. To put that another way, even for the conditions that have a prior probability of virtually zero (e.g., infectious diseases), China (and other Asian countries) are cranking out positive results that research groups in other countries can’t replicate.

This is all very disturbing, because it means that there are tons of bad studies out there, and the literature is very biased. Indeed, if you read the work of John P. A. Ioannidis, who has spent much of his career studying biases and problems in the scientific literature, you will find that the acupuncture literature matches pretty much every quality that he says to be cautious of. Here is a quote from the abstract of his famous paper, “Why most published research findings are false” (which I discussed here).

“In this framework, a research finding is less likely to be true when the studies conducted in a field are smaller; when effect sizes are smaller; when there is a greater number and lesser preselection of tested relationships; where there is greater flexibility in designs, definitions, outcomes, and analytical modes; when there is greater financial and other interest and prejudice; and when more teams are involved in a scientific field in chase of statistical significance.”

Nearly all of those conditions are met by the acupuncture literature. Indeed, an admittedly older review of the literature found that three fourths of acupuncture studies were of low quality, and low quality was associated with positive results (Ezzo et al. 2000). I have been unable to find a more recent study that actually estimates the percent of studies that are of low quality, but Deng et al. (2015) discussed many biases and methodological problems that are prevalent in the acupuncture literature, Linde et al. (2010) found that larger more robust studies tended to have fewer positive results than smaller studies (thus suggesting that much of the acupuncture literature is false positives from small studies), and the massive Ernst et al. (2011) review of reviews reported many low-quality studies.

Further, there is one really important source of bias that almost all acupuncture studies have. Namely, they aren’t double-blind. The person administering the acupuncture usually knows if they are giving real acupuncture or a placebo (e.g., sham needles or toothpicks). This could easily bias the results in a positive direction. Indeed, as I’ll talk about in a minute, it is well established that there is a huge placebo component to acupuncture, so it is entirely possible that slight differences in the behavior of the person administering the treatment could bias the results.

Numerous studies show that acupuncture does not work

Despite all the problems with the literature, we can still attempt to weed out bad papers and look at the randomized controlled trials with the highest standards and most rigorous methods. Here again, however, there are thousands of randomized controlled trials. As a result, it is very easy to cherry-pick studies, and citing individual studies is pretty pointless. Therefore, I am going to focus on meta-analyses and systematic reviews and ask that you do likewise and refrain from flooding the comments with cherry-picked studies. I’ve explained the hierarchy of evidence in more detail previously, but in short, meta-analyses and systematic reviews are the highest forms of evidence because they either attempt to review all relevant papers on a topic (for systematic reviews) or combine the data sets of multiple papers and run new analyses on those combined data sets (for meta-analyses). This, in concept, allows them to see overarching trends rather than statistical noise.

So what do these studies find? First, I want to acknowledge that studies comparing acupuncture to no acupuncture do show a “benefit” of acupuncture. That is hardly surprising, however, because virtually any treatment is “better” than no treatment. That is how placebo effects work (Finniss et al. 2010), and it is why the medical and scientific community defines effectiveness as being better than a placebo. To put it simply, if you do a test of a sugar pill vs no sugar pill, you will find a “benefit” of the sugar pill. Does that mean that the sugar pill is actually biologically active and is doing something useful? No, it’s just a placebo.

Understanding placebos is important, because as I will demonstrate in a minute, acupuncture has a strong placebo component (indeed, that seems to be the entirety of its effects), but many of the studies on it did not use a placebo (which is usually something like a sham needle that doesn’t actually penetrate the skin or even a toothpick). Thus, many of the studies supporting acupuncture were not properly controlled and are, therefore, unreliable. In contrast, numerous studies that were controlled have found that sham (placebo) acupuncture is just as “effective” as regular acupuncture. You can literally poke someone with a toothpick and get the same response as actual acupuncture, which is pretty damning evidence against acupuncture (here is one such example just so you can see what a study like that looks like: Cherkin et al. 2009).

Now, on to the actual reviews and meta-analysis. I can show you numerous systematic reviews and meta-analyses that fail to find that acupuncture performs better than a placebo (i.e., acupuncture doesn’t work). For example: Linde et al. 2011 (migraine prophylaxis), Davis et al. 2008 (tension head-aches), Lee and Ernst 2005 (surgery-related pain), Lee et al. 2005 (cancer-associate pain), Mayhew and Ernst 2009 (fibromyalgia), Zhang et al. 2010 (depression), Kong et al. 2010 (recovery from stroke), Smith et al. 2013 (inducing labor), Lim et al. 2006 (irritable bowel syndrome), etc. I could keep going, but hopefully I have made my point (also, see this list of Cochrane Reviews which paints a very bleak picture regarding the usefulness of acupuncture).

Nevertheless, you will, admittedly, not find it difficult to find meta-analyses and reviews that argue that acupuncture is actually more than a placebo. So, which do we trust? There are several things to consider here. First, we need to keep the aforementioned biases in mind. Second, we need to look for consistency. You may remember that this was one of my criteria for being convinced that acupuncture really works. As you may have guessed, however, that consistency is nowhere to be found (Ernst 2006). This was one of the chief conclusions of a very large systematic review of systematic reviews regarding acupuncture and pain (Ernst et al. 2011). Take a look at the tables in that paper. The reviews are all over the map. Indeed, the only condition for which there was consistent positive evidence from multiple high-quality reviews was for neck pain.

This is not what we would expect if acupuncture actually works. If it actually works, studies should consistently find that it works, but that’s not what we see. This is, however, exactly what we would expect if it is nothing but a placebo. We would expect a situation like this where (by a combination of chance and biases) some conditions occasional achieve positive results, but there is no consistency. Indeed, the fact that neck pain was the only condition with consistent results is very damning. Really think about this. Does it actually make sense that acupuncture works for neck pain, but not other types of musculoskeletal pain? No. That strains credulity. An editorial in the journal Pain (Hall 2011) described this well when the author said,

“Ernst et al. point out that the positive studies conclude that acupuncture relieves pain in some conditions but not in other very similar conditions. What would you think if a new pain pill was shown to relieve musculoskeletal pain in the arms but not in the legs? The most parsimonious explanation is that the positive studies are false positives.”

The final thing that must be considered here is the importance of effect size. You may recall that I specified that acupuncture should have a large effect size, and that Ioannidis (2005) warned that studies with small effect sizes are often spurious false positives. Thus, we should be cautious about saying that something works if it only shows a very small benefit.

There are two key concepts here that need to be understood to really evaluate effect sizes. The first is that P values (which are used to establish statistical significance) are probabilities, and they are often abused. The P value is the probability of getting a result as large or larger than the one you observed if there isn’t actually a difference in your groups. In other words, it is the probability that a result like yours could arise by chance (this assumes no bias or flaws in your experimental design). In biology, we usually say that something is statistically significant if it has a P value less than 0.05. In other words, if there is less than a 5% chance that a result like yours could arise by chance. Having a clear cut off like that has value, but people often make the mistake of treating 0.05 as a magical number that divinely arbitrates truth. Thus, if something has a P value of 0.06, it gets dismissed as non-significant, and if it has a P value of 0.04, it is automatically treated as a real result. That approach is silly. You should not be much more confident in a 4% chance than a 6% chance. Therefore, rather than blindly following P values, you should also look at confidence intervals or some other measure of variation, the actual size of the effect you observed, the sample size, etc. You need all of these pieces of information to really understand the result.

The other important concept here is that statistical significance and clinical or biological significance are not the same thing. Any difference between two groups becomes statistically significant with a large enough sample size, but that may not have any actual clinical relevance. It may be a difference that is too small to have any practical value (I talked more about P values and statistical significance here and here).

When we apply these concepts to acupuncture studies, we find many very small effect sizes. In other words, even when meta-analyses found a significant difference between sham (placebo) acupuncture and real acupuncture, the “benefits” of real acupuncture were quite small, often to the point that they have no clinical significance. To their credit, some authors have done a good job of acknowledging this. For example, an often-cited review and meta-analysis of acupuncture for pain (Madsen et al. 2009) stated,

“A small analgesic effect of acupuncture was found, which seems to lack clinical relevance and cannot be clearly distinguished from bias. Whether needling at acupuncture points, or at any site, reduces pain independently of the psychological impact of the treatment ritual is unclear.”

A review and meta-analyses for fibromyalgia made a similar statement (Langhorst et al. 2010):

“A small analgesic effect of acupuncture was present, which, however, was not clearly distinguishable from bias. Thus, acupuncture cannot be recommended for the management of FMS”

Nevertheless, not all authors have been this honest about their results, and the acupuncture literature is full of studies with tiny effects but grand claims (again, people seem to really want acupuncture to work). I want to talk about one particular study which is emblematic of this problem: Vickers et al. (2012) “Acupuncture for Chronic Pain: Individual Patient Data Meta-analysis.” When it came out, this study was spread wide and far by the press and was touted as concrete evidence that acupuncture works. When you actually look at the study, however, the situation is quite different. Both Dr. Steven Novella at Science-Based Medicine and Orac at Science Blogs have gone over this paper in detail, so I will give the short version.

This meta-analysis showed two things. First, both actual acupuncture and sham (placebo) acupuncture were “better” than no acupuncture (again, consistent with a placebo effect). Second, there was a very slight, but statistically significant difference between sham acupuncture and actual acupuncture. Let me be clear about what I mean by “slight.” On a pain scale of 1–10, the “benefits” of acupuncture vs. sham acupuncture were 0.5. In other words, they were too small for people to actually notice. Do you honestly think you can distinguish between a pain of 5.5 and 6.0? I doubt it. Indeed, this has actually been studied, and a review of pain in arthritis studies (Stauffer et al. 2011) found that a minimum of 0.7 was required for patients to detect it (usually more). In other words, a difference of 0.5 is not detectable by patients and is not clinically significant. Further, that difference is so tiny that it is extremely like that it could have resulted from biases, such as the fact that the trails were not double-blinded (i.e., the people administrating the acupuncture knew if they were giving a placebo or real acupuncture). It’s also worth mentioning that the study was conducted by the “Acupuncture Trialist’s Collaboration” so the authors had a fair amount of bias going into this.

Indeed, when you actually look at Vickers et al. (2012), it undeniably shows that almost the entire effect of acupuncture is from a placebo effect. Think about it, both sham and actual acupuncture had a large effect, but the difference between those two was imperceptibly small. In other words, the perceived benefits were due almost (if not entirely) to a placebo effect. Dr. Edzar Ernst, who has published many papers on acupuncture, stated,

“In my view, this meta-analysis is the most compelling evidence yet to demonstrate the ineffectiveness of acupuncture for chronic pain.”

 In the interest of fairness, the authors of the meta-analysis responded (Vickers et al. 2013), but their response is less than satisfactory. First, they do what many pseudoscientists do when criticized and incorrectly accuse their opponents of ad hominem attacks. They do eventually try to address the substance of the criticisms, but their rebuttals are less than convincing. For example, to address the argument that the slight difference could easily have been from a lack of blinding, they cited another paper by their group supposedly showing that acupuncture is better than sham acupuncture even when double-blinding is used (Irnich et al. 2002). At the risk of going down a side-tangent, I want to talk about this study for a second, because it once again nicely illustrates the type of shoddy science that is often used to support acupuncture.

To compare actual acupuncture with sham acupuncture in a double-blind design, one group received real acupuncture, while the other received lazer acupuncture (that’s a thing), but unknown to the administrator, the lazer’s bulb had been replace with a regular bulb that just made a red dot of light. This is not a good design for multiple reasons. First, using lazer acupuncture vs real acupuncture does not adequately blind patients, because in one treatment they feel pressure from a needle, and in the other, they don’t. Further, the fake lazer emitted a noise, thus making the different treatments obvious to patients. This is an awful design. To make things even worse, the person operating the lazer was always different from the person administering the actual acupuncture. Thus, the treatments were completely confounded with the person administering them, making the results impossible to interpret. It is entirely possible that the ones giving actual acupuncture simply had better bed-side manners, and that resulted in the difference (indeed, that seems likely, since they had years of experience, whereas the guy with the lazer wasn’t even certified). The point that I am trying to make here is that this is the type of evidence that people use to defend acupuncture. This type of garbage is the best that they have, and the fact that they think it is good evidence clearly reveals their biases.

Now, maybe you haven’t been convinced by any of this. Maybe you really desperately want acupuncture to work, and therefore you reject my arguments that the disagreement in the literature is a problem. If that is the case, then the best you could possibly say, with a really generous interpretation of the literature, is that there is wide-spread disagreement among studies, there are only a handful of afflictions with reasonably consistent results, and even for those, the benefits are so small that most people won’t notice them. Indeed, even the studies that argued that real acupuncture is better than sham acupuncture also found that almost the entire difference between acupuncture and no acupuncture could be explained by a placebo effect.

That is simply not compelling evidence, especially given the lack of mechanism and lack of evidence for even the existence of acupoints!

Think about it this way. Imagine for a second that we are talking about a pharmaceutical instead of acupuncture. Would you really take a drug if there was no known mechanism through which it could work, the physiological apparatus that it was supposed to interact with didn’t exist, there were numerous studies showing that it was no more than a placebo, and even the studies that argued that it works found such a tiny effect that you probably wouldn’t notice it? Would you honestly think that evidence was compelling?

Side effects

I want to quickly point out that acupuncture is not without side effects (Ernst et al. 2011; Xu et al. 2013). To be clear, most side effects are minor, but serious ones do occur, including organ trauma and even death. Your odds of having a serious problem are admittedly quite low, but why take the risk for something that is just a placebo? All actions have risk, and you need to weigh the risks against the benefits. In this case, the risk is admittedly low, but the benefit is non-existent (it’s a placebo), so why take the risk?

Counter arguments

Before I conclude this post, I want to briefly address some of the more common responses to posts like this (please don’t waste my time in the comments with arguments I’ve already addressed).


This is probably the most common response. People “know” that it works, because they tried it and felt better. Anecdotes are not, however, good evidence of causation. As I have explained at length, you probably felt better because of a placebo effect. Indeed, saying “I did X, then felt better, therefore X works” is a logical fallacy known as post hoc ergo propter hoc. It is not valid reasoning (details on why anecdotes aren’t good evidence here and here).

“It’s been used for thousands of years, so it must work”

This is known as an appeal to antiquity fallacy. The fact that something was used for a very long time does not mean it works. For example, tobacco was used medicinally for centuries before we found out that it is very harmful. Similarly, leeches, bloodletting, and countless other insane treatments were used for very long periods of time before being abandoned. I honestly don’t understand why people think this is a good argument. The fact that acupuncture predates science is an argument against it, not for it. Also, it is worth mentioning that China had actually largely abandoned acupuncture until gullible westerners took an interest in it.

“But some hospitals and doctors recommend it”

This is a form of the appeal to authority fallacy. For one thing, there are also many who agree that it is bunk. Additionally, in recent years there has been a disturbing infiltration of quack treatments into hospitals, medical schools, and medical organizations (largely driven by public demand for those treatments). This does not, however, validate those methods. For example, my university recently opened a healing touch clinic. Does that mean that there is actually good scientific evidence for magical healing touch therapies? No, it means my university figured out how to make more money from gullible people. You need actual evidence to show that something works, and as I have shown, that evidence does not exist for acupuncture (note a popular publication by WHO touting the benefits of acupuncture is often cited as evidence, but that publication was retracted in 2014 because it wasn’t based on evidence).

“A placebo effect is still an effect”

This argument asserts that even if acupuncture is just a placebo effect, it still helps people. It would take me an entire post to explain the problems with this in detail, but, here are some highlights. First, this argument is inane. Saying that something works as long as it produces a placebo effect makes no sense. It disregards fundamental concepts about how we conduct research and define effectiveness. Indeed, it is nothing more than a cop-out to dismiss a lack of evidence for a treatment that someone wants to believe in.

Second, this argument proposes that doctors should lie to their patients about the effectiveness of treatments that don’t actually work. That is a huge violation of ethical practices.

Finally, this argument misunderstands placebo effects, because they cover far more than simply thinking that you are going to get better, and it is not at all clear that placebos are worth much on their own. Dr. David Gorski at Science-Based Medicine explains all of this in more detail.

What’s the harm?

At this point in a post like this, many people fall back on simply asking, “what’s the harm? Does it really hurt anything if people want to believe in and use acupuncture?”

Yes, it does. For one thing, as stated previously, acupuncture does have adverse effects, including (rarely) death. Second, people may be inclined to use acupuncture instead of treatments that actually work. Third, I believe strongly in the benefits of knowledge, and continuing to act as if this pre-scientific hogwash is real and beneficial is antithetical to the goal of progressing our knowledge and understanding of the universe. This brings me to my final point: because the public wants acupuncture to be true and keeps spending money on acupuncture, scientists keep studying it. We have now wasted untold millions of dollars and decades of research on studying a treatment that doesn’t work. Imagine if all that time and money had been spent improving cancer treatments, studying neurological disorders, designing better anti-viral drugs, etc. There are so many better ways to spend that money, yet each year, millions more are wasted studying this placebo. That is a problem.


I will end with the quote from Friends of Science in Medicine’s review of acupuncture which summed things up better than I could,

“Acupuncture has been studied for decades and the evidence that it can provide clinical benefits continues to be weak and inconsistent. There is no longer any justification for more studies. There is already enough evidence to confidently conclude that acupuncture doesn’t work. It is merely a theatrical placebo based on pre-scientific myths. All health care providers who accept that they should base their treatments on scientific evidence whenever credible evidence is available, but who still include acupuncture as part of their health interventions, should seriously revise their practice. There is no place for acupuncture in Medicine.”

Related posts on evaluating the scientific literature 

 Suggested further reading 

Literature cited

  •  Cherkin et al. 2009. A randomized trial comparing acupuncture, simulated acupuncture, and usual care for chronic low back pain. Archives of Internal Medicine 169:858–866.
  • Davis et al. 2008. Acupuncture for tension-type headache: a meta-analysis of randomized, controlled trials. Pain 9:667–677.
  • Deng et al. 2015. Is acupuncture no more than a placebo? Extensive discussion required about possible bias. Experimental and Therapeutic Medicine 10:1247–1252.
  • Ernst 2006. Acupuncture — A critical analysis. Journal of Internal Medicine 259:125–137.
  • Ernst et al. 2011. Acupuncture: Does it alleviate pain and are there serious risks? A review of reviews. Pain 152:755–764.
  • Ezzo et al. 2000. Is acupuncture effective for the treatment of chronic pain? A systematic review. Pain 86:217–225.
  • Finniss et al. 2010. Placebo effects: Biological, clinical and ethical advances. Lancet 375:686–695.
  • Hall 2011. Acupuncture’s claims punctured: not proven effective for pain, not harmless. Pain 152:711–712.
  • Ioannidis 2005. Why most published research findings are false. PLoS Medicine 2:e124.
  • Irnich et al. 2002. Immediate effects of dry needling and acupuncture at distant points in chronic neck pain: results of a randomized, double-blind, sham-controlled crossover trial. Pain 99:83–89.
  • Kong et al. 2010. Acupuncture for functional recovery after stroke: a systematic review of sham-controlled randomized clinical trials CMAJ 182:1723–1729.
  • Langhorst et al. 2010. Efficacy of acupuncture in fibromyalgia syndrome—a systematic review with a meta-analysis of controlled clinical trials. Rheumatology 2010;49:778–88.
  • Lee and Ernst 2005. Acupuncture analgesia during surgery: a systematic review.
  • Pain 114:511–517.
  • Lee et al. 2005. Acupuncture for the relief of cancer-related pain—a systematic review. European Journal of Pain 437–444.
  • Li et al. 2015. What is the acupoint? A preliminary review of acupoints. Pain Medicine 16: 1905–1915.
  • Lim et al. 2006. Acupuncture for treatment of irritable bowel syndrome. Cochrane Database of Systematic Reviews 18:CD005111.
  • Linde et al. 2011. Acupuncture for migraine prophylaxis. Cochrane Database of Systematic Reviews (1):CD001218.
  • Linde et al. 2010. How large are the nonspecific effects of acupuncture? A meta-analysis of randomized controlled trials. BMC Medicine 8:75.
  • Ma et al. 2012. Epidemiology, quality, and reporting characteristics of systematic reviews of acupuncture interventions published in Chinese journals. Journal of Alternative and Complementary Medicine 18.
  • Mayhew and Ernst 2009. Acupuncture for fibromyalgia—a systematic review of randomized clinical trials. Rheumatology 46:801–804.
  • Ramey 2001. Acupuncture points and meridians do not exist. The Scientific Review of Alternative Medicine 5.
  • Ryan 2017. Acupuncture, ACC and the Medicines Act. New Zealand Medical Journal 130.
  • Smith et al. 2013. Acupuncture for induction of labour. Cochrane Database of Systematic Reviews 15:CD002962.
  • Stauffer et al. 2011. Definition of nonresponse to analgesic treatment of arthritic pain: An analytical literature review of the smallest detectable difference, the minimal detectable change, and the minimal clinically important difference on the pain visual analog scale. International Journal of Inflammation 2011.
  • Vickers et al. 1998. Do certain countries produce only positive results? A systematic review of controlled trials Controlled Clinical Trials 19:159–166.
  • Vickers et al. 2012. Acupuncture for Chronic Pain Individual Patient Data Meta-analysis. JAMA 172:1444–1453.
  • Vickers et al. 2013. Responses to the Acupuncture Trialists’ Collaboration individual patient data meta-analysis. Acupuncture in Medicine 31:98–100.
  • Wang et al. 2014. Positive results in randomized controlled trials on acupuncture published in Chinese journals: A systematic literature review. Journal of Alternative and Complementary Medicine 20.
  • Wu et al. 2009. Randomized trials published in some Chinese journals: how many are randomized? Trials 10:46.
  • Xu et al. 2013. Adverse events of acupuncture: A systematic review of case reports. Evidence-based Complimentary Medicine 2013:581203.
  • Zhang et al. 2010. The effectiveness and safety of acupuncture therapy in depressive disorders: Systematic review and meta-analysis. 124:9–21.
  • Zhou and Benharash 2014. Effects and mechanisms of acupuncture based on the principle of meridians. Journal of Acupuncture and Meridian Studies 7:190-193.
Posted in Vaccines/Alternative Medicine | Tagged , , , , , | 18 Comments

Dear Americans, stop using China and India as climate change scapegoats

Recent comments on a climate change post that illustrate this faulty argument.

I spend a lot of time on this blog debunking bad arguments, and I have previously devoted a lot of effort to debunking bad arguments against man-made climate change. There is, however, one extremely common argument that I have not previously addressed. I’ve been reluctant to deal with it because it is an argument about what we should do, rather than the facts of climate change. Nevertheless, it is extremely problematic and prevalent. Therefore, I think it is worth discussing.

The argument in question is made by Americans and states that there is no point in America reducing its greenhouse gas emissions because developing countries, India, China, etc. aren’t going to change their practices (you can see several examples of this argument in the screenshot from recent comments on my Facebook page). Underpinning this argument (and sometimes directly stated) is the assumption that America does a better job of dealing with emissions than other countries do, and countries like China are really the major guilty parties. This is one of those rare arguments where every aspect of it is wrong. The premises are incorrect, and even if they were true, the conclusion doesn’t follow from those premises. So, let’s talk about this for a minute.

A comparison of absolute greenhouse gas emissions among the biggest contributors. Any country that produced at least 5% of the global emissions is shown, with all other countries grouped into either Africa, Europe (without Russia), South America, or Other. The data are 2012 data from the European Commission Joint Research Centre.

First, we need to be clear about just how much America contributes to the world’s greenhouse gas emissions, because it is substantial. The USA produces roughly 14% of the world’s total greenhouse gas emissions. By comparison, the entire continents of Africa and South America combined produce only 11%. So those developing countries that proponents of this argument are so worried about aren’t the big contributors. Even when you combine a huge number of them, you don’t meet the emissions from the US. Indeed, India, which is one of the countries that nearly always gets singled out by this argument, only produces 7% of the world’s greenhouse gases. To be clear, that’s substantial, and it is a problem, but trying to shift the blame from the USA to India is insane, because the US produces way more greenhouse gases than India does. To be fair, China does produce a lot more than the US in terms of absolute numbers, but, as I’ll elaborate on below, China has a substantially larger population than the US.

If we really want to understand how much of a role each country is having in climate change, we also need to look at the data per capita (i.e., corrected for population size) rather than just the raw numbers. Looking at these data can become messy, because there are a bunch of tiny countries that, for various reasons, produce a lot of emissions per person. As a result, they score very high on per capita emissions, but are only contributing a tiny amount in absolute terms. The sensible approach is, therefore, to look at per capita emissions among the countries that are large contributors to the absolute amount of emissions. For the sake of this post, I set that threshold as countries that produce at least 1% of the world’s total greenhouse gas emissions. As you can see from the graph below, only 19 countries meet that criteria, and most of them aren’t countries that people would label as “developing.”

Greenhouse gas emissions per capita for any country that produced at least 1% of the world’s total emissions. I have colored the US, China, and India in red since they are the countries that are usually involved with the argument I am addressing. The data are 2012 data from the European Commission Joint Research Centre.

When looking at the per capita data for those countries, Australia and Canada are the worst offenders, and they absolutely should be held to account for that and should change their practices, but they only produce about 1.3% and 1.6% (respectively) of the world’s total emissions. So they are still fairly small players. The US, on the other hand, is a close third place for per capita emissions and, again, has very high total emissions. But what about China and India, the countries that people are so worried about? China is in 11th place, and India is in last place for per capita emissions (among countries who contribute at least 1% to the total emissions). Let me try to put the numbers this way: China has about 18.4% of the world’s population and produces 23% of the emissions. India has 17.2% of the population and produces 7% of the emissions. In contrast, the US has a mere 4.4% of the population but produces 14% of the emissions! To put that another way, on average, each American produces as many greenhouse gases as 2.2 Chinese people or 7.8 Indians. Again, to be clear, the emissions produced by China and India are a problem. I’m not suggesting otherwise, but stop pretending that they are the problem while simultaneously acting as if the US is some magical greenhouse gas utopia. It isn’t. The US is one of the worst offenders and produces far more greenhouse gases per person than either China or India.

Now that we have cleared up the actual numbers, let’s talk for a minute about the notion that the US is the only country that is taking action. This is blatantly false. Indeed, if you’ve paid even the tiniest bit of attention to world politics over the past few years, it should be obvious that this is false because of the Paris Agreement. This agreement was signed by China, by India, by all of those developing countries people are so worried about, etc. Do you remember which country backed out if though? I seem to recall it being the USA. Other countries (including China and India) are, in fact, investing in renewable energy. Similarly, China is implementing an emissions trading program to try to reduce their emissions. This notion that other countries aren’t acting is simply false.

Additionally, even if America was the only country that changed its actions, a large reduction in America’s emissions would still have global benefits, because, again, it is the second biggest contributor to climate change in absolute terms and one of the largest per capita. People seem to have this notion that climate change is a problem with a binary solution: either we fix it or we don’t, but that is an insane way to view the problem. Global warming is a continuum, and every 10th of a degree of warming matters and makes things worse. So, let’s imagine for a second that America drastically cuts its emissions but no other countries do, or perhaps they do so more slowly. What happens? Well, climate change still happens, but it occurs more slowly and/or doesn’t become as extreme. So, there would still be a global benefit even if America was the only country to take serious action (again, other countries are taking action, often more seriously than the US).

Finally, I want to ask, since when was, “other people were doing it too” a valid excuse for harmful actions? Let’s be clear here, how we should deal with climate change is really an ethical dilemma, not a scientific one. Science can tell us what is causing climate change, what we need to do to limit the warming, what happens if we don’t limit the warming, etc., but it can’t tell us what we should do, because that requires a moral judgement that science can’t make. Science does tell us, however, that the consequences of not taking action will be dire. They aren’t going to end modern civilization, but millions of people will die, and, indeed, thousands have already died as a result of climate change. Further, those negative effects will disproportionately impact the poorest members of our planet, even though they are the ones that contributed the least to the problem. I’m not going to enter into a lengthy philosophical rant here, but for me personally, that scenario is a problem. I personally think that human life has value and there is a moral imperative to minimize the loss of human life. Thus, I think that people need to realize that our actions have consequences, and regardless of what other countries do, the actions of Americans contribute to a problem that costs human lives. Now, maybe that isn’t an issue for you. Maybe you don’t value human life. I’m not here to convince you otherwise, but if you do value human life, then you need to take responsibility for your country’s actions rather than trying to pass the buck off to other countries. The fact that another country does something immoral does not justify you or your country doing something immoral.

In conclusion, I want to be clear that I am not attacking America, suggesting that it is entirely responsible for climate change, etc. This is a global problem and every country needs to take responsibility for their role in it. Further, countries like China and India do play major roles, but so does America, and Americans need to stop trying to shift the blame. It is a fact that America produces a disproportionate level of greenhouse gases and is a major contributor to climate change. It produces the second highest level of greenhouse gases in absolute terms, and per capita, it produces far more emissions than either China or India. So, this notion that other countries are the real culprits is blatantly false. America bears a huge portion of the blame for climate change. Additionally, it is insane to act as if America is the only country that is taking action against climate change, because it is lagging behind many countries, and countries like China and India are, in fact, making changes. There are certainly more changes that need to be made across the board, but again, that doesn’t mean that America shouldn’t do its part. Finally, even if America was the only country that was taking climate change seriously (which is clearly not the case), that still would not absolve America of its responsibility, and a reduction in America’s emissions would still be beneficial.

Data: I used the data from the European Commission Joint Research Centre. I originally chose this source because it had fairly recent global data for CO2 emissions (2016), but I ultimately decided it would be more meaningful to look at total greenhouse gas emissions (which only go up to 2012 at the time I wrote this). The patterns in both data sets are very similar and would in no way change my arguments, but feel free to play with the CO2 data if you want.

Related posts:

Posted in Global Warming | Tagged , | 23 Comments

Vaccines don’t “bypass the immune system”

I frequently encounter anti-vaccers who argue that vaccines are bad because they are “unnatural” and “bypass the natural immune system.” This argument is nothing more than an appeal to nature fallacy. Whether or not something is natural has no bearing on whether or not it is safe and beneficial, so I could stop right here, but let’s look at this argument further, because the core premise of this argument is not even true. Vaccines don’t “bypass” the immune system, if they did, they wouldn’t work. Rather, vaccines train your immune system to recognize deadly pathogens before you are exposed to them.

Before I can explain how vaccines train your immune system, you need to understand the basic concepts of how your immune system works. It can be broken into two broad categories: the innate immune system and adaptive immune system. Your innate immune system is, well, innate. It’s always there acting as your first line of defense. It includes things like your skin (which acts as a barrier to pathogens), mucosal surfaces, and non-specific immune cells like phagocytes and macrophages. That last qualifier is particularly important: the innate immune system is non-specific. It targets anything that does not belong in your body, but it is not specialized for particular pathogens. Think of it like your basic infantry. It’s a vital part of the military, but for particularly dangerous threats, you often need more specialized troops and weapons. This is where the adaptive immune system comes into play.

The adaptive immune system (aka acquired immune system) provides a targeted response that is specific for a given pathogen. You see, your immune system uses tiny molecules on the surfaces of cells to recognize friend (your body’s cells) from foe (foreign pathogens). These molecules, known as antigens, are specific for each type of cell, and your body can use them to engineer specialized cells that are specifically intended to fight a particular pathogen. Thus, when your body detects the presence of a novel pathogen (via its antigens), it triggers the adaptive immune system and begins producing B and T cells that are specific for that pathogen. Think of them like your special ops, snipers, stealth bombers, etc.

The catch is that because the adaptive immune system produces cells that are specific for a given threat, it can’t start producing those cells until your body has encountered the threat, and by that point, your body has already been invaded. In other words, it takes time for your body to mount an adaptive immune response, learn to recognize and target the invading pathogen, and produce sufficient numbers of the specialized cells. Meanwhile, despite the best efforts of your innate immune system, the enemy pathogens are replicating, spreading, and amassing a formidable army. Thus, for highly pathogenic diseases, by the time that your adaptive immune system is ready to go, the invaders have already claimed territories and your immune system is going to war, resulting in you being sick and potentially dying.

If you win the war and survive, your body will remember the disease and keep low levels of specialized troops circulating (via memory B and T cells). That way, a specialized force is ready to go if you are ever re-invaded by that pathogen in the future. This is what we know as “natural immunity.” It’s not perfect, and it can wear off overtime if your body stops producing and maintaining those specialized cells, but, combined with your innate immune system, it does a pretty good job of protecting you.

So, now that you understand the broad strokes of how your immune system works (it’s obviously far more detailed than what I explained), let’s talk about how vaccines fit into this. Vaccines present your body with the antigens of a given pathogen (usually via a dead or weakened form of the pathogen), along with an adjuvant to stimulate your immune system. This causes your adaptive immune system to mount a response even though you aren’t actually under attack. Thus, your body produces the specialized cells for fighting a given disease even though you don’t have the disease. Think of vaccines like scouting reports from spies that inform generals about the enemy’s plans and movements before the enemy attacks, thus allowing them to plan an appropriate defense. That is fundamentally what a vaccine does. It trains your adaptive immune system to be ready to fight a disease before you actually encounter the disease.

Further, following a vaccination, your body will continue to maintain a reserve of the specialized troops, just like it does after an actual infection. This is what actually protects you from diseases. It’s not the vaccine itself that protects you. Rather, it is the immune cells that the vaccine stimulates your body to produce (along with the antibodies some of those cells produce). Like natural immunity, the immunity from vaccines can wear off overtime, but a simple booster shoot will remind your body that this pathogen is important and cause it to continue to maintain adaptive immune cells that are ready to rapidly divide and fight the pathogen as soon as it enters your body.

Thus, as you can hopefully now see, vaccines don’t “bypass your natural immune system.” Rather, they stimulate your immune system and train it to recognize and fight pathogens before you are exposed to them. Indeed, they work exactly like “natural immunity” with only one important difference: natural immunity requires you to get the disease, whereas vaccines train your immune system without you getting the disease.

Suggested further viewing

If you want an excellent and much more detailed overview of the immune system, Hank Green’s three part Crash Course video series is about the best 30-minute introduction you could ever hope for (note: I didn’t watch these videos until after writing the post [I was looking for good videos to recommend to my readers], but he amusingly uses more or less the same military analogy that I used).
Part 1: Innate immunity
Part 2: Adaptive immunity (B cells)
Part 3: Adaptive immunity (T cells)

Related posts

Posted in Vaccines/Alternative Medicine | Tagged , , | 11 Comments

Extreme weather: The effects of climate change are already here

We are in the middle of yet another atypical hurricane season. Between hurricane Florence in America and typhoon Mangkhut in the Philippines and China, both hemispheres have been hit almost simultaneously by unusually strong storm systems. As a result, many people are again pointing a finger at climate change. This is not an unreasonable response, but it is one that we should be cautious about, because it is very easy to fall victim to the same logical blunder that often ensnares climate change deniers: confusing weather with climate. What we really need to know is whether there is a consistent pattern of increasing extreme weather events (spoiler alert: there is), so that is what I want to look at in this post (I’ll return to the topic of individual storm systems at the end). I’m going to briefly discuss the literature on extreme weather events to see if there is evidence that climate change is increasing their frequency and/or intensity. For the sake of brevity, I’ll just focus on three major categories of extreme weather: heatwaves, precipitation (both droughts and floods), and hurricanes (aka cyclones, aka typhoons; they are all the same type of storm, the names just differ in different parts of the world, but since most of my readers are American, I will refer to them all as hurricanes throughout).

Before I begin, I want to point out that this is a very important topic for understanding the consequences of anthropogenic climate change, because the extremes are potentially the most dangerous aspect of climate change. If you think about heatwaves for a second, this should make sense. Summers are already hot, but for the most part, they are bearable. They only really become a problem when we have consecutive days of abnormally hot weather (i.e., heatwaves). Thus, having a summer where the temperature is consistently 1°C above normal is inconvenient, but not critical (strictly in terms of the heat itself). However, having a summer with heatwaves that are more frequent and more intense is a far more serious dilemma. That type of summer is far more likely to cause heat strokes and various other problems. Similarly, having an average increase in rainfall (with low variation) is not nearly as problematic as having an increase in the number of massive, flash flood-inducing downpours. So, if we are going to talk about the potential damage and cost (economically, physically, and environmentally) of climate change, it’s important to discuss the extremes.

I’d also like to briefly state that the evidence is extremely clear that we are the primary cause of the current warming. Discussing that evidence is beyond the scope of this post, but I have previously done so here and here, as well as debunking most of the common arguments to the contrary here. Please read those posts before commenting with an argument that it’s not our fault.


Let’s start with the easy one. As its name suggests, global warming is resulting in a planet that is, on average, warming. Currently, the four hottest years on record are 2014, 2015, 2016, and 2017 (not in that order), and if current trends continue, 2018 will join their ranks, meaning that all five of the top five hottest years will have occurred in the past five years. Based on these increases in mean temperatures, it is hardly surprising that in many areas heatwaves have also been increasing and that increase is linked with global climate change (Klein Tank and Konnen 2003; Della-Marta et al. 2007; Tanarhte et al. 2015; Habeeb et al. 2015). Indeed, Perkins et al. (2012) found that, globally, the intensity, frequency, and duration of heatwaves is increasing. In other words, heatwaves are becoming hotter, we are experiencing more of them, and they are lasting longer (Habeeb et al. 2015). Further, other research has found that not only are heatwaves increasing, but the areas that are affected by them are expanding (Russo et al. 2014).

All of that is really bad, because despite common perceptions to the contrary, heatwaves are actually the most dangerous natural disaster in terms of human mortality. According to the CDC, in the US, heat kills more people than tornadoes, floods, lightning, or hurricanes. Indeed, the death tolls during large heatwaves can be staggering. For example, during 2003, Europe experience a record-breaking heatwave (far beyond expectations for natural weather patterns; Schar et al. 2004; Stott et al. 2004) that resulted in over 70,000 deaths (Robine 2008), with nearly 15,000 deaths in France alone (Argaud et al. 2007)! Let that sink in for a minute. This heatwave was so bad that it killed nearly 15,000 people in a single country.

To be clear, none of this is fearmongering, speculation, or “liberal propaganda.” These are simple facts. People are dying as a direct result of climate change, and the situation will continue to get worse if we don’t take action (Meehl et al. 2004; Luber et al. 2008; Lelieveld et al. 2016).

Extreme precipitation

 One of the things that people often find confusing about climate change is that the effects are different in different areas. Indeed, some areas are expected to experience increased precipitation (to the point of flooding), while others are expected to experience increased drought. Sometimes people jump on this fact and claim that climate scientists are simply making things up and claiming that everything is climate change no matter what weather we experience. but such claims are untrue. If you actually read the literature and look at the models, they clearly predicted beforehand that the patterns of change will not be uniform (i.e., some areas will have droughts while others have floods; though the net effect should be increased precipitation globally). Further, we aren’t running around arbitrarily claiming that changes in precipitation are due to climate change. Rather, we are very carefully studying the changes in wind currents, evaporation rates, etc. so that we understand the underlying mechanisms that are driving the changes. Finally, despite common claims to the contrary, our observations are actually pretty consistent with models’ predictions (Dai 2012; more sources and details here).

Describing these mechanisms in detail is far beyond the scope of this post, but two major patterns seem to be at play. First, many areas will experience more of the extremes of their typical weather patterns (Dai and Trenberth 1998). In other words, if you live in a fairly wet area, it is probably going to become wetter, and if you live in a fairly dry area, it is probably going to become drier. Again, this situation of exaggerated extremes is problematic. Dry areas already struggle with not having enough water, while wet areas already struggle with having too much of it, and climate change is expected to make both of those situations worse. The second pattern, which is related to the first, is that, in many cases, more precipitation is expected at high latitudes, while less precipitation is expected in the arid sub-tropics (Trenberth 2011).

So, what are we actually observing? In short, there is a net increase in precipitation globally (Alexander et al. 2006), and some areas are experiencing more extreme downpours (Dai and Trenberth 1998; Groisman et al. 2005; Trenberth 2011), while dry areas are experiencing more droughts (Dai and Trenberth 1998; Dai 2010; Trenberth 2011). These downpours and droughts in turn are resulting in increased floods and wildfires (respectively), increased damage to crops, increased damage to ecosystems, increased damage to property, increased loss of human life, etc. (Rosenzweig et al. 2001; Milly et al. 2002; Flannigan et al. 2009; Carnicer et al. 2010; Schlenker and Lobell). Further, I want to make it clear again that scientists aren’t running around arbitrarily blaming climate change for these events. We have carefully studied the underlying mechanisms of these precipitation extremes and found that the current trends are unlikely to be natural and are linked to human-induced increases in temperature (Held and Soden 2006; Allan and Soden. 2008; Min et al. 2011).


These storm systems are probably the ones that get the most attention in the press and general public, but they are, unfortunately, some of the hardest to study. This is because they are infrequent (resulting in small sample sizes per year) and because record keeping for them has been surprisingly inconsistent, making it difficult to look at long-term patterns. Having said that, we have sufficient data from the past few decades to draw some conclusions. Before I get to those though, I want to talk about scientists’ expectations, because most models don’t actually predict an increase in the total number of tropical storms (in some cases they actually predict a slight decrease). Rather, the prediction is that the storms will increase in intensity, and really intense storms will become more common. In other words, the total number of hurricanes per year should stay the same or go down slightly, but we expect more of those hurricanes to be very large, powerful storms (e.g., category 4 and 5 hurricanes). As with everything else that I have talked about thus far, that is problematic because the extremes are where most of the damage comes from. Having the same total number of hurricanes but more category 4s is worse than having a greater total number of hurricanes with mostly category 1s and 2s.

So, with all of this in mind, let’s once again look at what we have actually found. Walsh et al (2016) published a fairly recent review of this topic, so I recommend reading them for more details and sources, but in short, what we’ve found is that there is a general increase in both storm intensity and the proportion of storms that are really powerful (e.g., 4s and 5s), but the total number of hurricanes has not increased (Emanuel 2005; Elsner et al. 2008; Holland and Bruyere 2014). Also, the trends are more pronounced in some areas than others, with the North Atlantic basin (i.e., the one that affects the US) showing the strongest patterns. Another interesting and alarming result is that hurricanes are moving further away from the tropics and towards the poles (Kossin et al. 2014). In other words, as the planet warms, the tropics are expanding north and south of the equator, and, as a result, powerful hurricanes can strike further north and further south than they could previously. Thus, cities that have never had serious hurricane problems may now be faced with strong storm systems.

Update 2019: There is increasing evidence that hurricanes are also “stalling” more frequently. In other words, they are staying in one area for longer, thus resulting in increased damage (Kossin 2018; Hall and Kossin 2019).

As a final note, the damage caused by these systems is also increasing not only because the storms are becoming more intense, but also because sea level rise is resulting in increased storm surge and flooding.

The influence of climate change

 Before I conclude this post, I want to return briefly to the topic of blaming particular storm systems on climate change, because that situation is actually more complex than most people give it credit for. In short, we can never say with 100% probability that climate change caused a particular extreme weather event, but, based on all of the data that I have discussed, we can confidently say that climate change is making these events more likely, and for any particular event, it is likely that climate change played a role.

Let me use smoking as an example. If a regular smoker is diagnosed with cancer, you can never say with 100% certainty that smoking caused the cancer. It is always possible that they would have developed cancer even if they never smoked. However, because we know that there is an overarching causal relationship between smoking and cancer, we can say that smoking very likely contributed to their cancer and that, in general, smoking rates contribute to cancer rates. The same thing is true with climate change and storms. Because of the known causal relationships between temperatures and extreme weather events, for many extreme events, we can state that climate change likely played a role in them and that, in general, increased climate change is resulting in increased extremes.

Additionally, in the case of climate change, we can often go even further. By examining natural trends, our influence on the climate, and the causes of particular storm systems, we can often calculate the probability that a given system would arise absent our influence (and, conversely, how likely it is that our actions played a role). Indeed, several of the studies that I have cited throughout this post have done that. For example, as I mentioned earlier, when scientists examined the 2003 heatwave in Europe, they found that it was unlikely based on natural patterns (Schar et al. 2004) and that our actions have doubled the risk of such events (Stott et al. 2004). So, while we should be cautious about blaming everything on climate change, there is often very good evidence that particular events were probably influenced by our actions.


In short, there is very clear evidence that extreme weather events are increasing, and that increase is linked to climate change (which we are causing). Heat waves, floods, and droughts are all on the rise, and they bring with them heavy economic, environmental, and health burdens, with thousands of people dying as a result of them. Further, the intensity of these events is increasing as well as their frequency. Similarly, for hurricanes, storms are becoming more intense, and the strongest, most dangerous categories are becoming more common. This is a very real and dangerous consequence of our actions.

Again, this is not fearmongering or “liberal propaganda,” it’s not something that will only happen in the distant future, and it certainly isn’t a Chinese hoax. This is real, and it is happening right now. People are already dying as a direct result of what we are doing to the atmosphere, and those death tolls will only become worse if we don’t immediately take action to stop the climate from changing any further. I rarely include calls to action in my posts (other than encouraging people to fact check and think critically), but this topic is far too important for me to end the post without one. We need to start taking climate change seriously and stop relying on fossil fuels, even if it costs some jobs, increases taxes, etc. The cost of not taking action will be far, far higher than the cost of taking action, both economically and in terms of human lives. Thousands have already died because of climate change, and thousands more, probably millions more, will die if we don’t change our actions. We have the technology right now to make a huge difference, we just need to invest in it, and that means that you need to take personal responsibility in your daily choices and, perhaps most importantly of all, you need to contact your governmental representatives and tell them that this needs to be a priority. Then, you need to vote accordingly.

Note: In all likelihood, switching energy sources would actually result in a net increase in jobs and net increase in the economy, but even if that wasn’t true, the jobs of a few coal miners and bank accounts of rich oil CEOs aren’t worth the lives of the thousands of people who will die because of climate change.

Related posts

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Posted in Global Warming | Tagged , , | 10 Comments

Is it likely that alternative medicine works? The importance of prior probability

Prior probability is basically just the plausibility of a result, given everything else we know about the universe. In other words, when evaluating a hypothesis or a study, you should weight your confidence in the result not only on the characteristics of the study in question, but also on how likely it is that a given result is true given our prior knowledge. To put that another way, science always builds on previous research, and the results of previous studies can often give us a good idea of whether or not a given result is plausible, before we actually conduct the study. People often act as if ideas and hypotheses exist in a vacuum and should be considered in isolation from everything else, but that isn’t how science works. It always builds on existing knowledge, and new ideas and results have to be evaluated in light of what we already know. Thus, it is often the case that we know enough about the system in which a hypothesis exists to have a really good idea of whether or not that hypothesis is correct before directly testing it, and, in some cases, our knowledge of a system is comprehensive enough that it is not even necessary to directly test the hypothesis.

To give a silly example, imagine someone tells me that pouring Mountain Dew into my car’s engine will improve its performance. Even without actually testing that hypothesis, I can reject it with a very high degree of confidence. I know enough about how cars work to know that it is almost certainly wrong. In other words, this idea conflicts with what we already know about how cars work, therefore it has a very low prior probability, and there’s really no good reason to bother testing it. Further, ignoring this suggestion that Mt Dew is good for cars isn’t being “close-minded,” “ideological,” “dismissive,” etc. There’s simply no good reason to think that it is right, and plenty of good reasons to think that it is wrong. Science inherently has to use what we already know as a starting point, and throwing everything that we know out the window to chase absurd suggestions is a substantial waste of time and money.

At this point, I can hear people screaming at their computers that science has to be based on evidence and experimental results, and you’re absolutely correct, but nothing that I have said disagrees with that. Prior probabilities have to be based on previous research, or else they are going to be very inaccurate probabilities. I’m not suggesting that we arbitrarily decide what is and is not true. Rather, I am simply pointing out that, thanks to decades of scientific research, we know enough about how the universe works to know that some ideas are patently absurd without directly testing those ideas. Further, keep in mind that science itself is an inherently probabilistic endeavor. Even after we directly test a hypothesis, we can’t say with 100% confidence whether the hypothesis is true or false. Rather, we can simply say that it is likely true or false based on the existing evidence.

Let me give another trivial example to illustrate this further. As a herpetologist, people often send me blurry photos of reptiles and amphibians that they want me to identify. Now, imagine someone sends me some blurry pictures that were taken in northern Michigan, and they tell me that they think that these photos show a population of broad-headed skinks (a lizard species). Without even looking at those pictures, I could say that they almost certainly are not broad-heads, and I could say that, because northern Michigan is well outside the known range of broad-heads. In other words, everything that we know about broad-heads says that they aren’t in Michigan. Therefore, the prior probability that these photos are of broad-heads is essentially zero. We’d have to be very wrong about our understanding of that species for those photos to be broad-heads. Nevertheless, it is, of course, always technically possible that our knowledge is in fact wrong, but we’d need far more evidence than some blurry photos before we could reach that conclusion. I’d want to see the lizards themselves and, ideally, test their DNA.

With all of that in mind, let’s talk about “alternative medicine” (aka complementary medicine, aka CAM). There are countless alternative treatments out there, and while many of them haven’t been studied (or only have a few studies), others have been extremely well-studied and have hundreds of publications (e.g., homeopathy and acupuncture). Looking at the evidence for these well-studied treatments can, however, be confusing, because while there are tons of studies saying they don’t work, there are also some studies saying that they do, sometimes even including systematic reviews. There are really good ways to evaluate the studies themselves (details here, here, here, here, and here), but prior probability is also quite useful. Further, evaluating the studies themselves obviously doesn’t help for the treatments that lack studies, but prior probability is still helpful.

that's not how this works memeLet’s take homeopathy as an example. As I’ve written about before (here and here) homeopathy relies on some pretty strange assumptions. First, it is based on the concept that “like cures like.” In other words, it treats a condition with something else that should cause the symptoms of that condition. For example, according to homeopathy, since coffee can cause people to have difficulty sleeping, coffee should also be useful for treating people with insomnia, because coffee causes the same symptoms as insomnia (I’m not making this up; homeopaths literally make supposed sleep aids from coffee beans). If that sounds crazy, good. It is crazy. We know a lot about biochemistry and how the human body works, and we know that it doesn’t work that way.

Second, homeopathic treatments are made by doing numerous serial dilutions, with each step making the active ingredient increasingly dilute. According to homeopathy, this works because diluting something actually makes it stronger. Again, that’s now how things work. One of, if not the, most fundamental concepts in toxicology and pharmacology is that the dose makes the poison. Everything is safe at a low enough dose (i.e., if it is diluted enough) and everything is toxic at a high enough dose. We know this. So, this concept that diluting something makes it stronger flies in the face of basic chemistry. As I’ve argued before, if you think that diluting something makes it stronger, try diluting some beer and let me know if it takes more or less of it for you to become drunk.

Third, because homeopathic solutions are often so dilute that they literally no longer contain a single molecule of the active ingredient (i.e., they are nothing but water), homeopathy also claims that water has memory and somehow retains the properties of the active ingredient even though the active ingredient is no longer there. Again, that’s not how chemistry works. Water doesn’t retain the properties of things it previously came in contact with.

So, when you add it all up, homeopathy is extremely implausible because it requires three different assumptions, each of which disregards basic facts about the universe. The odds that we are so fundamentally wrong on all three of those topics are very low. Therefore, homeopathy has an extremely, extremely low prior plausibility. A huge chunk of modern science would have to be wrong for it to be right. This means that we have really good grounds for dismissing it without further investigation. It also means that we would need some truly extraordinary evidence before we could conclude that it actually works. A few small studies simply won’t cut it. We would need many, massive studies with exquisite experimental designs and a very consistent pattern of positive results among them before we could say that homeopathy works.

Homeopathy has actually been well studied, but when you look at the results of those studies, you don’t find anything even approaching extraordinary evidence. There are lots of studies that found negative results (i.e., that it doesn’t work) and the studies that found positive results usually had small sample sizes and only found moderate effects. That is simply not sufficient evidence for a topic with such a low prior probability. Remember, false positives do occur even when a study was conducted correctly. That’s why we need to look for consistent patterns of evidence and consider the prior probability of a given outcome. The less plausible the conclusion, the more consistent and powerful the evidence needs to be.

Moving beyond homeopathy, we find the same type of implausible conclusions throughout alternative medicine. Acupuncture is based on mythical meridians and the pseudoscientific concept that there is good and bad energy. Similarly, “treatments” like reiki and healing crystals rely on unsubstantiated nonsense about energy and frequencies. Detoxes and cleanses ignore how your liver works, and the acid alkaline diet ignores how homeostasis works. I can keep going here. Ear candling, magnet therapy, earthing, reflexology, cupping, using chiropracty to treat disease, etc. All of these ignore basic facts about how the human body functions, while making absurd assumptions for which there is no evidence. Thus, they all have a very, very low prior probability, and we would need some extraordinary evidence before we could conclude that they work, and in the absence of that evidence, we can confidently move them into the rubbish-bin of failed ideas, because they conflict with everything that we already know about physiology, physics, chemistry, medicine, etc.

To be fair, some alternative treatments do have a higher prior plausibility than the treatments I’ve talked about thus far. Herbs, for example, are kind of a wash when it comes to prior probability. We know that many plants produce chemicals that have effects on our bodies, and we know that sometimes those effects are beneficial. So, the basic concept behind herbs makes sense, and there is a good prior probability that some of them work. However, that does not mean that there is a high prior probability for any one particular herb. Basically, what this means is that we need studies before we can conclude that an herb works, but the studies don’t need to be anything extraordinary. A few reasonably large, well-constructed studies are sufficient (assuming that there are consistent results among those studies), and in the absence of those studies, the rational position is to say that we don’t know if a given treatment works, rather than saying that a given treatment probably doesn’t work. Thus, this is a very different situation from something like homeopathy where we would have to be fundamentally wrong about the universe in order for it to work.

Now, at this point, you may be wondering why I am picking on alternative medicine instead of talking about conventional, or so-called “western” medicine (aka medicine). The answer is simply that our system for developing new drugs and treatments is specifically designed to maximize prior probability before we ever get to human trials. First, drugs are designed based on a detailed knowledge of biochemistry, which is far better than alternative medicine’s strategy of making a treatment based on anecdotes, tradition, and, often, superstition. Second, before being tested on humans, new drugs go through in vitro and/or animal trials. Drugs that fail those tests are deemed to have a low prior probability of working and are discarded, whereas drugs that work safely and effectively in those trials have a higher prior probability of being safe and effective in humans. To be clear, we still need good studies before we can conclude that they do actually work, but, as I tried to explain earlier, we don’t need the type of monumental, paradigm-shattering evidence that we need for many alternative treatments.

Finally, I can foresee those who believe in alternative medicines responding to this with the comment, “but [insert anecdotes].” So let me forestall that. Anecdotes simply are not good evidence of causation and, as such, don’t help you much with prior probability. As I’ve explained at length before, saying, “I took X, then got better, therefore X made me better” is a logical fallacy known as post hoc ergo propter hoc. It is an invalid line of reasoning. You could have improved because of regression to the mean, something else you took, chance, another type of placebo effect, etc. Further, you can find anecdotes for literally any treatment. There are, for example, many people who use anecdotes to argue that you should be drinking bleach and/or turpentine, but, somehow, I doubt that you place much weight on those anecdotes.

Nevertheless, you might try to argue that anecdotes aren’t good evidence of causation, but they do shift the prior probability. In the case of something like herbs, where no fundamental scientific concepts are being violated, I will grant you that they slightly improve the prior probability, but only to the extent that, if a scientist is going to test some herbs, it makes sense to start with the ones with lots of anecdotes behind them. I would not agree that anecdotes shift the prior probability enough to be useful for interpreting the results of the subsequent studies. Further, for things like homeopathy, acupuncture, etc. the prior probability is already so insanely low that anecdotes don’t make any difference.


In short, prior probability is simply the concept of using previous scientific knowledge to assess how likely it is that a given hypothesis or result is actually true. From that, we can  determine the strength of evidence that is necessary before we reach the conclusion that a given result is correct. If a result is consistent with what we know about the universe and makes sense based on previous research, then it has a high prior probability, and only needs moderately strong evidence before we can conclude that it is likely correct. In contrast, a result that flies in the face of basic scientific concepts would have a very low prior probability and would require extraordinary evidence before we could accept it as likely being true. Much of alternative medicine falls into that later category. It often ignores basic facts about science, makes absurd assumptions, and invokes fictitious concepts about energy, frequencies, etc. Indeed, many alternative treatments fly in the face of what we already know about the universe and have such a low prior probability that we can be reasonably confident that they don’t work without actually testing them.

Additionally, although I focused on alternative medicine for this post, the concept of prior probability is widely applicable. Countless topics like astrology, psychics, tarot cards, etc. have a very low prior probability based on everything we know about the universe. Therefore, they can be confidently dismissed as nonsense until such time as extraordinary evidence arises in their favor. Again, to be clear, if that evidence arises, you have to consider it, but you are not required to take the positions seriously or treat them as plausible until extraordinary evidence in their favor is found. To put that another way, we know enough about the universe to know that something like astrology is almost certainly wrong without actually testing astrology.

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Posted in Vaccines/Alternative Medicine | Tagged , , | 5 Comments

Courts don’t determine scientific facts

Most people have probably seen the recent news that Monsanto has been ordered to pay $289 million following the ruling by a California jury that Monsanto’s glyphosate (a.k.a. Roundup) is dangerous and likely contributed to Dewayne Johnson’s cancer. I could write many lengthy posts about why that ruling is wrong. I could talk about the numerous scientific studies that failed to find evidence that glyphosate causes cancer (e.g., this large, long-term cohort study with over 50,000 participants that wasn’t funded by Monsanto and failed to find an association between glyphosate use and cancer among farmers [Andreotti et al. 2017]). I could talk about the well-established fact that the toxicity of glyphosate is quite low. I could talk about the fact that multiple well-respected scientific bodies have examined the evidence and concluded that it does not suggest that glyphosate causes cancer. I could also talk about how the one dissenting scientific report (i.e., WHO’s IARC report) cherry-picked their evidence and reached a conclusion that has been widely criticized by the scientific community. Plenty of other pages have, however, already done all of those things, so I won’t spend more time on them here. Rather, I want to discuss why trials like this one are inherently problematic. Citing court rulings is an extremely common tactic among science deniers (anti-vaccers do it all the time), but it is not a logically valid tactic because courts don’t determine what is and is not a scientific fact.

The first major problem is simply that juries don’t consist of experts in the relevant scientific field. As I’ve talked about before, science is complicated. It takes years of carefully training, study, and hands-on experience to learn everything that you need to know to be able to properly evaluate scientific evidence. The notion that an untrained jury is going to master that over the course of a trail is absurd. Further, it is especially ridiculous when you consider that courtroom conditions inherently involve two opposing sides arguing as if they have equivalent merit. To put that another way, it is extremely easy to cherry-pick evidence to make it look like the science isn’t settled on an issue or, worse yet, like the scientific consensus is the opposite of what it actually is, and in a courtroom, a lawyer will do precisely that. They are obligated to argue in favor of a given position, regardless of whether that position is actually supported by the evidence.

Let me try an example. Imagine that there is some issue with your heart that you want diagnosed, and someone suggested to you that it might be because a particular aspect of your diet (i.e., you eat X, and they think X is bad for your heart). So, you take two approaches to figuring out whether your diet is the cause. In the first approach, you get multiple respected scientific organizations to examine the scientific evidence that X can lead to heart problems. These bodies of highly trained and experienced experts spend months or even years systematically examining the studies on this topic. The look at all the evidence that they can get and, ultimately, they conclude that there is no compelling evidence for X contributing to heart problems.

For the second approach, you construct a jury using the same criteria as in a court, then you get two lawyers to debate the issue as in a courtroom. One of them tries to convince the jury that X does cause heart problems, and the other tries to convince the jury that X does not cause heart problems. Rather than systematically examining all of the evidence, both lawyers cherry-pick evidence that supports their position, attempt to play on the jury’s emotions, bring in cherry-picked “expert” witnesses, etc. At the end of the trial, the jury concludes that X does cause heart problems (which is the opposite of what the scientific committees found).

Which conclusion seems more reliable to you? The one that was arrived at by experts spending months carefully and systematically examining all of the available evidence, or the one that was arrived at by non-experts basing a decision on a comparison of two extremely biased representations of the evidence? I think that the answer to that is pretty obvious.

To be clear here, I’m not saying that scientists are infallible or that the conclusions of scientific organizations are definitive statements of reality. That would be an appeal to authority fallacy. Rather, my point is that the courtroom system is fundamentally flawed and unreliable for determining scientific facts. The fact that a jury decided that X causes Y is completely and 100% irrelevant in any scientific debate. It has no bearing on reality, and you would be crazy to trust it instead of relying on numerous high-quality studies and reviews and meta-analyses of those studies that were systematically assembled by teams of experts. Whether or not something is a scientific fact has to be determined by actual research, and a jury’s opinion about that research is irrelevant.

Posted in Nature of Science, Rules of Logic | Tagged , , , | 54 Comments