The rising prevalence of autism: lessons learned from the Flynn effect

Average IQ scores during the last 8 decades have increased by some 25 point. This is an incredibly huge gain observable throughout the whole world, including developing countries.  If you were able to travel back in time to the turn of the century a person of average intelligence then would appear to be mentally retarded using modern standards and norms. This phenomenon was noted by several researchers including Richard Lynn, a British Professor of Psychology who has written extensively on controversial issues related to racial and national differences in intelligence. However, the person who has done the most research on the subject of IQ gains over the last century is James R. Flynn. Some people have called the increase in IQ over time phenomenon the Lynn-Flynn effect but the majority abbreviate the same as the Flynn effect.

James R. Flynn is a native of Washington DC who later on in life immigrated to New Zealand. Curiously, his research emphasis was intelligence testing, but his PhD was in political sciences rather than psychology. His conclusions and perspectives on this phenomenon have been summarized in popular books including: “What is Intelligence?: Beyond the Flynn Effect” published in 2007, and “Are we Getting Smarter?: Rising IQ in the Twenty-First Century” published in 2012.


James Flynn (1934-  )

To summarize the Flynn effect, there is a clear trend indicating that individual’s IQs have gained about 3 points per decade. The gain is seen regardless of intelligence tests used and has been noticed throughout all examined countries of the world. Again, such a change in IQ is astronomically large!

The Flynn effect stands in clear opposition to the view of researchers that claim that genes are your destiny, or that intelligence is defined primarily by your genetic constitution, or even that intelligence is fairly stable throughout your lifetime. There is plenty of evidence from the literature to support many of the latter arguments. Modern studies now seem to tie intelligence to a large number of genes (Note: similarly autism is tied to about 5,000 risk genes, that is one out of every 4 genes from our genome). So critics of the role of genetics in intelligence welcomed with open arms the Flynn effect because such drastic changes over a few generations could not occur as the sole effect of genes.  A change in IQ worldwide suggests that social factors are somehow related to the phenomenon.

If you are thinking the same way I am thinking (hopefully you are), you will notice an analogy to the rising prevalence rates in autism.  In both instances noted changes denote a significant increase that can’t be the effect of genetic changes alone.  It is impossible for genetic mutations to create evolutionary changes worldwide over the short span of 2 or 3 generations. Naysayers, people trying to explain away the phenomenon, have considered that appropriate norms (whether intelligence tests for the Flynn effect or diagnostic criteria for autism) have changed considerably during the studied period in question. However, numerous studies have shown that the numbers do not add up and we are left with a significant increase despite changing diagnostic criteria.  Other possible explanations for the Flynn effect include how modern industrialized nations offer exposure to enriched environments since early childhood to our brooding population. Society is changing recruitment of the workforce towards jobs that require better visual skills (see Thinking Like Einstein by Thomas West). Consider the role of television and video games in the everyday life of our children.  Consider the types of toys that were available 80 years ago and those that are available now. While playing video games our children are practicing cognitive skills unavailable to our generation.  Also reflect on the general nutritional status of our population and the availability of supermarkets across the country.  Read the science and math books your high school child takes for his/her school and compare the same to the ones you used.  The Flynn effect is not unexpected, we can see it in everyday life.

Now consider other analogies between the Flynn effect and autism. In both the role of society seems to play a major role. Our environments have changes, we are now exposed to byproducts of industrialization (e.g., pollution) and to new practices (e.g. use of repeated ultrasounds during pregnancy).  It is interesting that the new DSM-V criteria accept diagnosis of autism spectrum disorders at later points in life whenever environmental exigencies surpass the capacity of the subject.  This means that a person working within limited capacity at younger ages may display symptoms much later when first going to mainstream school or even later on when joining the Army. This fact would increase the total number of people with a diagnosis of autism spectrum disorders that were otherwise previously confined to more severe cases – those who were symptomatic in the first few years of life.


Another important factor is that the Flynn effect is greatest in the bottom 10% of IQ scores. Meaning that IQ has increased within the population, because those individuals at the lower tail end of the IQ distribution have improved their scores. Otherwise the highest IQ quartile of individuals have not gained as much.  This is somewhat similar to autism where parts of the increase in prevalence (now 1 in 50) may be due to the inclusion of a fraction of individuals, primarily ASD children who were previously unrecognized (Blumberg et al., 2013).

The rise in prevalence in autism and the Flynn effect still await explanations. As many issues that draw upon a variety of social sciences disciplines it is doubtful whether we will be able to obtain concrete answers. There will always be groups of skeptics. However, the questions these phenomena pose makes it of utmost importance that we pursue them.  Curiously acceptance of the role of society and diminished role of genetics have been readily welcome and entertained in the scientific arena for the Flynn effect.  The same phenomena in autism has drawn dire criticisms, polarized researchers, and remains a contentious issue. In autism a line has been drawn in the sand which provides little or no room for a compromise. Maybe we could stand to learn from other areas of science.


Blumberg SJ, et al. (2013) Changes in prevalence of parent-reported autism spectrum disorder in school-aged U.S. children: 2007 to 2011-1012. National Health Statistic reports 65.

11 Respuestas a “The rising prevalence of autism: lessons learned from the Flynn effect

  1. Hi Manuel Casanova –

    Interesting article.

    I find the rise in immune mediated disorders to have similar properties; we observe more asthma, more diabetes, more MS, more IBS, more food allergies. The same explanations of improved awareness and better diagnostic methods are trotted out (don’t worry!) but when we evaluate far reaching changes we have implemented the past few decades; i.e. C-Sections, antibiotic (over) use, acetaminophen use during infancy, our population level fattening, the move from rural to urban environments, we see that those are risk factors for developing auto immune disorders.

    We *also* observe curious immune alterations in the autism population. What a crazy coincidence!

    I won’t discount that large chunks of the ‘increase’ are diagnostically driven, but the dogma that the all of the increase is an artifact, or some nebulous *small* amount of the increase *might* be real, is a dangerous fantasy; it is comforting, but mandates that all of the changes we have implemented aren’t have any effect.

    How many times will we gain more powerful filters to evaluate relationships, find that our wisdom at detecting unexpected relationships wasn’t quite up to speed when we started implementing [practice X], before we start to wonder if maybe the soft scientists are the last people we should be trusting to answer the incidence question?

    – pD

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  2. I have used the immune argument frequently in the past trying to make the same point. Unfortunately not many people have taken notice. I tried the Flynn effect as something that was less polarizing but from which we could learn some lessons. I have found it very difficult for other scientist to think outside of their comfort zone. Thank you for the comments.

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  3. Well, it is kind of sad that at this point anyone should still be unable to recognize that epigenetic mechanisms can drastically change the way genes are expressed (and that these can indeed occur over the span of as little as 2 generations). So the argument that, since genetics can not change so fast, autism can’t be linked to genetics is actually quite disappointing. You want an explanation ? We are conducting a large scale long term world wide experiment changing body chemistry through food (and there has even been genetically tampered food for quite some time now), drugs (prescription and non-prescription), pollution, unhealthy ways of life (stress) etc. Where is it going ? The next century or so will tell. As an engineer I will also tell you this: complex systems are essentially non-linear in behavior so that small changes today can propagate creating big changes as time goes by and they are nearly impossible to predict (that’s actually a very promising field for research). Needless to say that every human body is a complex system and that the other living things of this planet as well the natural environment surrounding them all add up to make things even more complex and non-linear.

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    • The point of the blog was that genetics by itself (without considering environment) can’t be the answer to the rising prevalence of autism. Hopefully the message was clear. The meaning that one may give to words is biased by one’s own background. However, the statement stands as correct and I doubt anybody would dispute the importance of the environment.
      There are many articles in the literature about how the body,
      and more specifically the brain, behave as complex systems. I, as well as many other people, have written articles and chapters in this regard. A good reference article is: Casanova MF. Cortical organization: a description and interpretation of anatomical findings based on systems theory. Transl Neurosci. 2010;1(1):62-71
      How these precepts are applied to brain organization, aging, and evolution is an interesting subject. An article expanding on this, and more specifically as to how these laws apply to autism, is:
      Casanova MF, El-Baz A, Switala A. Laws of conservation as related to brain growth, aging, and evolution: symmetry of the minicolumn. Front Neuroanat. 2011;5:66
      Thanks for your comments. Our points of view are not so far apart as we stress the importance of the same phenomena..

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  4. So, basically, if we understand well enough how the brain works we will be able to fix it ? Wouldn’t it be much simpler to go back to what used to work before ? I believe that is pretty much what autistic children’s parents are doing right now (I read a lot of ‘detox’ discussions). Anyways, if we fail in both regards in the long run, eventually nature itself will force our hand.

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  5. I am not sure where you are getting your conclusions, e.g., if we understand well enough how the brain works we will be able to fix it? You may be suggesting that I have said something similar, but this is not the case. I really was not able to follow the logic, specially bringing detox into the discussion. If I am missing something please feel free to elaborate in an email. I appreciate your comments.

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  6. The way I see it, discussion unfolded along two main streams: genetics / environment (epigenetics) and complex systems. Obviously austistic children’s brains require ‘fixing’ if they are to behave ‘normally’. Thus, when you argue that research is currently approaching the brain from a complex systems perspective I infere that the goal is to understand how it works and treat abnormal functioning (including autism). Also, you argue that genetics is not causing the increase in austism ocurrence. Thus I argued detoxing because it means removing environmental factors (epigenetics) and also because I hear about it all the time from most parents in the ARI support group (they’re doing it!). Is it working ? I don’t know. Particularly, I don’t think it is that simple, that once epigenetic changes are installed you can reverse them simply by removing the environmental pressures that caused them in the first place. Probably, we all should detox before we put more innocent children in this world. I can speak only for myself: in terms of drugs I take none unless I’m convinced it is absolutely necessary (for exeample, the flu ? I take nothing, no painkillers, decongestants etc.), in terms of pollution, stress, bad food … well, I do whatever I can and feel it’s better. But, finally, to improve the latter, awareness and joint effort are required.

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  7. Thank you for the explanation. I now understand better your way of thinking. As an aside, I do not believe in detoxification or for that matter in the causative role of postnatal environmental exigencies. Most of our work in terms of neuropathology reveal abnormalities during brain development, primarily as cells migrate to the cortex. maybe I will expand on this in a future blog. Thank you for your patience with me.

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    • «As an aside, I do not believe in detoxification»
      Whereas I believe in evidence, and the evidence of my own experience and thousands of others is that detoxification works (subject to competent protocols applied to those who have a toxicity problem in the first place). Of course I’m not talking of the Scientology or wacko popular twits’ «detox»scams here.

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  8. On the subject of Flynn Effect AND autism increase….There is a very relevant new publication, titled «Rising–falling mercury pollution causing the rising–falling IQ of the Lynn–Flynn effect, as predicted by the antiinnatia theory of autism and IQ»
    If you email to my address there I can send you a free copy.
    Basically elemental mercury is an antiinnatia factor (reduces gene expression and thus causes autism and raised IQ) and consequently atmospheric mercury vapour has caused the Flynn effect, and the change to non-gamma-2 amalgams has caused the autism increase. Merc also causes all those immune allergy problems. And that is only a part of the greatest medical catastrophe ever.
    A huge amount more info on this has been suppressed for a decade by the utterly corrupt «peer review» censorship system but will be revealed in another way very soon.

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    • By the way, the autism increase began just before 1980 dob, whereas the Flynn increase began at least 100 yrs earlier then started going down again circa 1980 dob. Both due to mercury vapor! Everyone breathes the atmosphere whereas only some have harmfully high intakes from parental amalgams in underventilated rooms. There’s a lot more (seeriouslly amazeing such as you would never guess) to this I’ve discovered.

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