Rain Points to Environmental Trigger for Autism

Prevalence higher in areas with more precipitation

MONDAY, Nov. 3 (HealthDay News) -- There is a higher prevalence of children with autism in areas with higher annual precipitation rates versus areas with lower rates of rainfall, pointing to an environmental trigger for the condition, according to an article published in the November issue of the Archives of Pediatrics & Adolescent Medicine.

Michael Waldman, Ph.D., of Cornell University in Ithaca, N.Y., and colleagues analyzed data from counties in California, Oregon and Washington on prevalence rates for autism, and mean annual precipitation.

In counties in all three states there was a positive association between rates of rainfall from 1987 through 2001 and prevalence of autism in 2005, the researchers report. In Oregon and California counties with a regional center, there was a higher prevalence of autism for birth cohorts born when there was relatively heavy precipitation in their first three years of life, the investigators found. The authors suggest increased television viewing (which may have adverse health effects of vulnerable children), vitamin D deficiency as a result of less sun exposure, and greater exposure to chemicals used indoors as possible explanations for the association.

"Our results are clearly not definitive evidence in favor of the hypothesis," the authors write. "But the results are consistent with the hypothesis, and, therefore, further research focused on establishing whether such a trigger exists and on identifying it is warranted."

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