Why has autism gone up so much? Has autism gone up so much?

Of all the questions that readers of Freakonomics ask me to explore, understanding the explosion in autism is at or near the top of the list. I haven’t read the original study, but this news report offers an interesting hypothesis about the rise in autism: older fathers. Don’t tell Dubner I’m citing Wikipedia, but there is a nice entry there devoted to the frequency of autism.

Because the term autism covers such a wide spectrum of diagnoses, even pinning down the simplest questions like “how much has autism risen?” or “what fraction of the rise is due to changing standards of diagnosis?” are hard to answer.

I’ve been asking myself lately whether an economist could bring anything useful to the study of these questions? So far I’m not sure what the answer is to that question.


And peanut allergies. What's going on with those? NOBODY had them when I was a kid, now it seems like every third baby has one.


as to how economists may be usefull in this kin of research: if you can think up of a valid instrument for age of father at marriage i would be an obvious improvement on the endogeneity ridden estimates reported in the cited paper (I would expect men with higher levels of human capital to marry later, and thus have kids latter. If HK is related to some unobservable characteristic (say "mild autism") the estiamte will be biased upwards.


A poorly formed question: Is there such a thing as a fad rating (how popular something is at a given time), to what extent does its fad rating effect the frequency of its occurrence, the frequency of its study, and the frequency of its reporting. How are the diagnoses of Autism, ADHD, and so on, subject to the current fashions of diagnosis. Surely there are historical antecedents, ("neurosis", for example) of diagnoses that had their day and now are scarcely mentioned.

The "mildly autistic" children I've met recently reminded me very much of what we used to call "weird kids"


110phil, great question on the peanut allergies, I know exactly what you mean. Never heard of it once as a kid, now it seems to be in every classroom.


The American healthcare system is on the verge of a total collapse and people want to entrap the mind of one our best economists into pursuing autism and peanut allergies. I wonder if drug companies would like to see Stephen walk in and ask for all the stastistics related to drug trials? Probably not. I wonder if Oncologists would get upset if Stephen were to ask for all the buried files of the dead patients whose chemotherapy and radiotherapy put them in the ground a little faster while the taxpayer had to pay for that 'cutting edge' treatment? Are hospitals really even safe? Stephen, I hope your not wasting your time on this trivial tripe. Your country needs you. The biggest criminals are selling drugs to dying people that actually don't do them a lick of good. Merck is the tip of the iceberg. I double dog dare you Dubner.


Check the frequency of vaccinations particularly the meningitis vaccinations. There was already note on this in Time Magazine about Autism, may 29 2006. If you have data on vaccinations per area and check that against the rise of autism, something will show up


The rise in allergies in the developed world are caused by parents keeping their kids too clean at a very young age. This causes their kids to fail to develop a fully fuctioning immune system. Allergies, eczcema, asthma etc are all caused by oversensitive immune response systems.

Let you kid get dirty folks!

Stephen J. Dubner

there's also been speculation that autism is found at a higher rate in twins than in singletons:


when i first heard this, i wondered about fertility drugs among other potential causes. but it's possible that the older-father theory dovetails with the twin theory also.


What's the difference between a drunk and an Alcoholic? Drunks don't go to those stupid meetings.

I'm sorry if that offends anyone. I'm not trying to say AA meetings are stupid, making light of alcoholism, etc., etc. Just trying to make a point about LABELS.

The rise in these varying ailments, conditions, syndromes, and so on has a lot to do with labelling and blame. Behaviour that in the past might just have been a little bit, let's say, "eccentric" can now be labelled with a scientific term. Suddenly, something new is created, something new exists. That's not to say that there aren't people out there who have autism, peanut allergies, and the like, but isn't there a bit of cultural/social cache that goes with being labelled (or labelling yourself) as something different? And if you want to be completely cynical, there's probably a fair amount of financial benefit from certain diagnoses.



As to the question of what an economist might contribute to the study of autism rates, I'd point at the following issue as a starting point: I have a friend whose son was clearly "not right". After lots of agonizing, and lots of testing, he was diagnosed with Asperger's-type autism.

Now, it's well-known that diagnosis of anything can often bring tremendous relief to someone who has been suffering with a nameless problem, but in this case, the relief was something different: it was relief that he QUALIFIED for state-funded programs to help autistic kids. That meant physiotherapy, speech therapy, a special preschool, swimming lessons, and more.

I don't deny that this boy will really benefit from these programs, and I'm glad he's getting them. And, obviously, his parents don't want him to be autistic. But... there must be many cases (autism, and other syndromes or diseases), where an upswing in prevalence reflects the pushing of borderline cases into diagnosis, in order to qualify people for benefits. If that's not economics, I don't know what is!



My 3 year old son has multiple life threatening food allergies, so I have read a little in the area. The current prevalence of peanut allergy (PA), conservatively, has been estimated at over 1% from a number of recent studies. As I understand it, there is no conclusive evidence that the prevalence of PA has increased in recent years. There certainly seems to be raised awareness of the issues, which is no bad thing.

Although the causes of food allergies are not well understood, Stuart's comment that the rise in allergies in the West is because kids are kept "too clean" is not supported by any of the literature I have read. And I can assure Rich that having a food allergic child gives me no social or cultural cache (or cachet for that matter).


"trivial tripe"? I simply cannot believe these comments. Out of the 11 above I count 4 that dismiss autism as some sort of fad, suggesting that parents actively wish their children would be diagnosed as autistic, etc. As a father whose daughter was diagnosed with autism I am incredibly angry and insulted and can't understand where this backlash is coming from (probably worth a study of its own).

Having a child with autism brings with it a feeling that cannot be understood by someone unless it is experienced. To have someone you love unconditionally not be able to speak to you, make eye contact, know when you're there or gone ... never mind things like reading, writing, playing and all the other things kids can do. A parent with a autistic child needs to put in ten times the amount of work as another parent, without getting back the simple rewards that a small child can give.

I can see why this subject is the one that people find too trivial for Stephen's attention, but sumo wrestling in Japan is not.



There's a theory I've always found interesting about non-autistic people with an autistic phenotype being more likely to become scientists, mathematicians or engineers. A study (link below) establishes a link between having austism and being related to engineers.

The corollary to this theory is that the surge in autism rates could be a symptom of the growth of high-tech industries. Geeks carrying genes with autism associations are increasingly brought together into corporations and communities where they meet other geeks of the opposite sex carrying similar genes, and have children with significantly higher likelihoods of being autistic.



Sander: The hypothesized link between vaccination and autism has been thoroughly investigated and totally discredited.

It was proposed that thimerosal, a chemical used in many vaccines that contains a small amount of mercury, could do harm to the mental development of small children. This was expanded to suggest that it could be linked to a rise in autism rates.

Biologists were always skeptical, since the mercury in thimerosal is in smaller quantity and in a safer form than other sources of mercury children are regularly exposed to in their normal environment.

There was never any solid science supporting the hypothesis, and since then many studies have concluded that it is totally unfounded, and there is no link between vaccination and autism.

The conspiracy theorist and anti-vaccination people still cling to the idea, but it cannot be considered a scientific argument.


"Geeks carrying genes with autism associations are increasingly brought together into corporations and communities where they meet other geeks of the opposite sex carrying similar genes, and have children with significantly higher likelihoods of being autistic."

Doubtful. Male geeks, whether they've got autism genes or not, represent a genetic dead end because few of them are able to find women. Geekiness in a man drives away women like nothing else. Obesity, baldness, having an obnoxious personality, none of those things are as remotely as severe a barrier to finding women as is geekiness. Men who devote their lives to geeky pursuits - Trek, D&D, Warcraft, LOTR - are overwhelmingly single.


As a male geek (a big fan of Trek, LOTR, role playing, Warcraft, and how could you possibly forget Star Wars) with three children I have to wonder if you are speaking from empirical or anecdotal grounds.

I didn't go that route, but you could similarly hypothesize that the tech boom raises the earnings potential of geeks, which in turn raises their prospects for marriage. And there we have another potential tech boom to autism link.

In college, a friend of mine did an internship as a software developer for Microsoft, and made this observation while attending a large Microsoft social function: "You know, looking around at all these guys' wives, you can really tell which ones held out until they were rich."


"As a male geek (a big fan of Trek, LOTR, role playing, Warcraft, and how could you possibly forget Star Wars) with three children I have to wonder if you are speaking from empirical or anecdotal grounds."

There are exceptions to every rule. I would caution against drawing sweeping generalizations from your particular case.

"I didn't go that route, but you could similarly hypothesize that the tech boom raises the earnings potential of geeks, which in turn raises their prospects for marriage."

That's possible, but men shouldn't have to *buy* women for marriage. There's little consolation for a geeky man who is of more modest financial means. Even the last-ditch method of buying mail order bridge can cost many thousands of dollars, not to mention the fact that new federal rules have greatly restricted the industry.


Mango: The link between vaccinations and autism has been thoroughly researched is your belief. The fact that with real autism (not autistic behavior) there is a inflammation of the 4th ventricle and a swelling of the frontal lobe has been reported (Time article) The question is how can this be inflamed?? The diseases that these kids are subjected too are partly these vaccinations. When you just investigate a substance in this vaccination you cannot conclude that the whole vaccination is harmless. But collecting data on incidence in areas where there is a lot of vaccination against areas where there is no vaccination, and comparing this to the incidence of autism will give an idea. A new theory on the swelling of the frontal lobe is that it is compensation for the underdevelopment of this area, i.e. compensation of the body to the inflammated area of the brain. It is a matter of continuing to ask questions and not wanting the answers. Why is that part of the brain inflammated??????



The Skeptic's Dictionary is a wonderful resource for all matters pseudo-scientific.



I was one of the people who sent you an Email (April 2006) hoping you would explore this topic. I wrote:

I'm not sure if this falls into your area of Freakonomics but the Autistic Controversy and the use of Thimerosal in Vaccines is a potential blockbuster against the CDC.It would be great to have some independent eyes look at the figures and determine if there is a correlation between Autism and Vaccines. Estimates now say that 1 in 166 new births will result in some form Autism. Prior to 1990 it was 1 in 10,000 births.

You responded very timely and I agreed with you that diagnosis has played a major part in the rise. However, when I continue to look at the numbers a corresponding rise in other disorders does not equate to the rapid rise in Autism if it were just diagnosis.

"Evidence of Harm" by David Kirby is an excellent resource that looks at both sides of the issue. I urge you to read or talk to Mr. Kirby
From the book,

Over five years ago, the federal government disclosed that most American children were being exposed to levels of mercury in vaccines above federal safety limits. Since then, officials moved to phase out mercury from childhood vaccines, and to determine if thimerosal exposure in infants could cause autism and other neurological developmental disorders. To date, neither goal has been fully attained

Since retiring I work with Autistic Spectrum Disorder Children. Our grades 1-4 has seen a staggering amount of children with ASD symptoms.

Why should you look into this topic?

An independent look at the data may bring some helpful conclusions or at least better questions. The CDC and NIH have datbases of cases. Howver, THE CDC will not provide all the information.

You looked at Sumo Wrestlers and Teachers, why not ASD and Thimerosal?

The best reason, You and Dubner both have young children and if your children go to public school, stop in yourself to the special education room and look for yourself.

Ask your friends or relatives if they know of some child with ASD.

Thanks again,