Finally, Hard Evidence Against The “Autism Epidemic”?
The idea of an ‘autism epidemic’ has a lot of people very worried.
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
-
http://www.blogger.com/profile/12033918835169823548 M.J.
-
http://www.blogger.com/profile/13033764030940406139 ioianthe
-
http://www.blogger.com/profile/06647064768789308157 Neuroskeptic
-
http://neurobonkers.com Neurobonkers
-
http://petrossa.me/ petrossa.me
-
http://www.blogger.com/profile/06647064768789308157 Neuroskeptic
-
Anonymous
-
http://www.blogger.com/profile/04233143008146729664 Peter Hildebrand
-
Anonymous
-
http://neurobonkers.com Neurobonkers
-
Anonymous
-
http://www.blogger.com/profile/10860246538349067232 Lindsay
-
http://www.blogger.com/profile/10860246538349067232 Lindsay
-
Anonymous
-
http://www.blogger.com/profile/02843717286012748265 seymourblogger
-
http://www.blogger.com/profile/09484166723075799719 Dan Mirman
-
http://www.blogger.com/profile/17417022296647288072 grumpy-xl
-
Anonymous
-
http://www.blogger.com/profile/17686665037607780553 RAJ
-
http://www.blogger.com/profile/17417022296647288072 grumpy-xl
-
Anonymous
-
Anonymous
-
Anonymous
-
Anonymous
-
Anonymous
-
Anonymous
-
Anonymous
-
Anonymous
-
Anonymous
-
Anonymous
-
Anonymous
-
http://www.blogger.com/profile/06647064768789308157 Neuroskeptic
-
http://www.blogger.com/profile/05026223483117357541 usethebrains godgiveyou
-
Anonymous
-
Anonymous
-
http://www.blogger.com/profile/06647064768789308157 Neuroskeptic
-
Aggie
-
Anonymous
-
http://www.blogger.com/profile/12033918835169823548 M.J.
-
Anonymous
-
Anonymous
-
Anonymous
-
http://www.blogger.com/profile/06647064768789308157 Neuroskeptic
-
http://www.blogger.com/profile/12059415005282675289 Paula
-
Black Book doc
-
Black Book doc
-
Balck Book doc
-
http://www.blogger.com/profile/17789702672617697592 ilovetrash
-
Black Book doc
-
http://www.blogger.com/profile/06174157687212464551 Lucilyn labajo
