The Spatial Structure of Autism in California, 1993-2001 - Incite at Columbia University

We determined there are certain geographical areas in California where newborns are more likely to develop autism. Using a large dataset from California we found that children born in a cluster, centered on West Hollywood, roughly 20 by 50 kilometers, were four times more likely to develop autism than children born elsewhere in California. These children were two times more likely to have autism than those born to mothers over age 40 a factor strongly associated with increased risk of autism. This cluster persisted after parental age was adjusted for. It is not known what causes these clusters and is a subject of further research.