Is there an "autism epidemic?" Neuroskeptic is, well, skeptical.
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 epicenter is L.A.; there's actually three overlapping hotspots centered on Santa Monica, Alhambra and North Hollywood.Read more here: http://neuroskeptic.blogspot.com/2012/12/finally-hard-evidence-against-autism.html
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 pediatricians, 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.