Autism May Be Associated With Precipitation Levels

Children living in counties with higher levels of annual precipitation appear more likely to have higher prevalence rates of autism, according to a new report. The results raise the possibility that an environmental trigger for autism may be associated with precipitation and may affect genetically vulnerable children.

Several potential explanations exist for the positive association, the authors note. Precipitation may be associated with more indoor activities, such as television and video viewing, that affect behavioral and cognitive development. The increased amount of time spent indoors also may expose children to more harmful chemicals, such as those in cleaning products, or decrease their exposure to sunshine, which helps the body produce vitamin D. "Finally, there is also the possibility that precipitation itself is more directly involved," the authors write. "For example, there may be a chemical or chemicals in the upper atmosphere that are transported to the surface by precipitation."

Because there is no direct clinical evidence of an environmental trigger for autism that is associated with precipitation, the results are preliminary, the authors note. However, "further research focused on establishing whether such as trigger exists and on identifying it is warranted," they conclude.