No one disputes that diagnosed rates of autism have increased enormously over the past 15 years or so, around the world. However, other people write it off as essentially a cultural phenomenon: we’re getting better at detecting the disorder and more willing to label kids as having it.

I subscribe to the latter view, but there’s very little hard evidence for it. To prove that diagnostic changes have occurred, rather than a true increase in autism, you’d have to know what would have happened to today’s kids, say, 20 years ago. Would they have been diagnosed? We have no way of knowing. At least not until someone invents a time machine.

However, a new study just out offers a valuable new perspective on the debate: Spatial clusters of autism births and diagnoses point to contextual drivers of increased prevalence.

According to authors Soumya Mazumdar and colleagues, there’s a zone of high autism prevalence in California, areas where kids aged 0-4 years old are more likely to be diagnosed with the condition. The epicentre is L.A.; there’s actually three overlapping hotspots centred on Santa Monica, Alhambra and North Hollywood.

In these clusters, autism rates are between 2 and 6 times higher than the rest of the state.

Now an interesting thing about these areas was that they’re rich in paediatricians, autism advocacy organizations, and money. In other words, there’s better access to health services and probably more awareness of autism. This is suggestive evidence that the reason lots of kids get diagnosed here is about diagnosis, not autism per se.

But the blockbuster result is that children born outside the cluster, who later moved home into one, had a higher chance of getting a diagnosis than those who stayed out. The effect was smaller than for kids born inside the hot zone, but it was significant.

That’s also consistent with the idea that the clusters are clusters of diagnosis, not autism.

It’s not proof. You could argue that there’s some toxic chemical, say, present in the rich parts of L.A. that causes autism, even if you move into the toxic area only at age 3 or 4, and that’s been getting worse recently, leading to rising rates.

But it seems a stretch. What’s the chemical? And why hypothesize one, when the diagnostic services hypothesis nicely accounts for these findings? As the authors say:

The findings reported in this article do not fully reject the possibility that environmental toxicants drive some of the risk of autism … since there are a plethora of possible toxicants, it is impossible to falsify all hypotheses that researchers have started to explore.

Mazumdar S, Winter A, Liu KY, and Bearman P (2012). Spatial clusters of autism births and diagnoses point to contextual drivers of increased prevalence. Social Science And Medicine PMID: 23267775

This post first appeared at Neuroskeptic.

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13 Responses for “Finally. Hard Evidence Against the Autism Epidemic?”

  1. john says:

    Super interesting.

    Wonder what we’d see if we mapped diagnosis patterns for asthma?

  2. John M says:

    The toxin may be cocaine or other drugs. Wealthier people also have children later in life–past their prime. Too much missing info here to draw any conclusions.

  3. maithri says:

    Wonder if this will service as impetus for researchers to better utilize support from parent-advocates moving forward.

  4. defenestr8 says:

    Wasn’t this clustering evidence also used in another paper as support for paternal age? Back in 2010 the WSJ covered a couple articles using California data.

  5. The clusters found earlier in the Silicon Valley were also reported to be more affluent. Along with this many are more likely to stay current on new developments and recommendations from the USDA, medical and heart associations. Often both parents work and the children are provided easy to fix breakfast foods that in fact lack several of the nutrients required for good brain development and function. Many in my recent study of more than a thousand were avoiding cholesterol and animal fats for the chiild’s diet and were following recommendations for a more vegetarian or vegan diet that must be supplemented to avoid malnutrition. I accept that more are being diagnosed but if you talk with teachers they will confirm that more of the children are experiencing these symptoms than a couple of decades earlier. Adequacy of the child’s diet is very rarely a consideration in most research on autism even though the parents know the child is a picky eater, and in many of these children, they get to choose their own diet.

    • levins says:

      using iphone, apologies on mass typos!

      its a chemical called TCE. nike missile sites were everywhere for the cold war. worldwide! overlay nike missile site maps with autism rate maps. ironically, if the shoe fits… in silicon valley there are nike sites directly above crystal springs reservoir. tce is easily airborne and blows from the west year round. south korea niw 1 in 25 boys and rising? completely covered in nike sites. the entire , also open aquaducts, etc.

      its really simply. all these sites were highest elevation. recipe for distaster. i guarantee there are records of how much tce was delivered. request how much was delivered, more importantly how much was removed when they shut all sites down in the 70s. think they dumped it? read this:

      must read this gem circa 1982! all the water tables are polluted already. its tough to remove, if not impossible.

      google maps some locations. converted to housing, schools, soccer fields!!! oh my.

      its all here.

    • Kristy says:

      As a mother of a four year old son with autism
      I don’t believe diet is causing this epidemic. which it clearly is an epidemic
      It is more likely exposure to toxins in the environment in our food and in our homes. It also may be do to the vaccination schedule and the amount of vaccinations we are now giving children at such an early age. I ate very healthy while pregnant and my son has always eaten very healthy as well i got lucky in the way that he doesn’t have to many sensory issues food related and you can sneak any vegetable into a daily fruit smoothy that being said
      Diet can help these kids in there recovery. alot of these kids have gi problems many i believe go undiagnosed
      My son has been food sensitivities to gluten and dairy and that was an easy one to test and figure out since alot of them do have the same food issues.
      But he kept scratching at his chest and back of his neck and had what i was told was “”pica”" he would literally fight me over eating chalk
      I was told these are just simtoms of autism
      I felt horrible when i found out that he had acid reflux he is non verbal and he wanted that chalk for a reason
      Some times we have to keep searching for answers to why and how do i fix this. I’m not done searching.
      suggesting that it is the parents fault for letting them eat fruit loops and candy is not helping the thousands of mothers like me looking for answers

  6. levins says:

    my fingers dont move nearly as fast as my brain. this gets me wound up since i figured it out… cover LAs wind pattern map, with autism map, and nike site map, and water supply map… you can do similar things to explain every hotspot worldwide. i cant say im happy to have found this. its not good.

    its apparent to me ( i was born in 77, siblings born 70, 71, etc) that the effects get progressively worse every generation. i.e. mostly aspergers high functioning for people aged 35+ and then progressing to the debilitating effects we’re starting to see.

  7. levins says:

    are you familiar with the “freeway proximity” association? thats where the missile sites are. rings around every major metro…

  8. luther says:

    California areas of affluence (i.e. Santa Monica) have better access to pediatric health care and have greater awareness of the indicators suggestive of autism, than those in less affluent areas (i.e. South Central). This statement could be made related to most any pediatric medical concern, pick one: teenage pregnancy, STD’s, measles, chicken pox, influenza, etc…, etc… What does that prove? As far as better awareness it is less obvious of a flawed thought process, but in the 1970′s the prevelance was one in ten thousand, now it’s one in eighty-eight. Oh well it’s better diagnosis. Ok use that logic on any other random topic just to see how flawed that sounds. Lets pick Train Wrecks. In the 1970′s when we saw a Train Wreck, we would identify it as a Train Wreck. The prevelance was one-in ten thousand of all accidents. Now we have gotten so much better at corectly identifying Train Wrecks when we see them the prevelence is one in eighty eight of all accidents. Yea right….. Almost reminds me of a South Park episode where the police officer (authority figure) says “Move along, nothing to see here….” as all hell is breaking loose around him. To me it still seems like an epidemic. I strongly believe autism will continue to become more,and more, and even more prevelant until America as a whole recognizes it for the epidemic it is, and takes agressive action and research to try to solve it. Respecting reasearch, tons of money are being dumped into genetic reasearch to find a genetic cause for autism. I wouder how sound that logic is when all disorders, current known to have a genetic cause (down’s syndrome, cystic fibrosis, color blindness, etc…) have only grown in prevelence comparable to population growth. Maybe if the rate goes to one in ten, or some other wildly desperate situation, will we take alarm.

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