Researchers at Cornell University have found that children in Washington, Oregon and California who live in rainy counties have higher reported rates of autism than those in drier areas.
Kids living in Western Washington, which gets about four times as much precipitation as the eastern part of the state, had autism rates that ran twice as high as those in the east.
The research, published this week in the Archives of Pediatrics & Adolescent Medicine, raised the possibility that heavy rainfall forces children who are vulnerable to autism indoors, where there is greater exposure to cleaning chemicals and television, and less exposure to sunshine and the vitamin D it produces.
The study does not confirm a cause-and-effect link between rain and autism. However, Cornell professor Michael Waldman, lead author of the report, suggested it was an important step toward discovering environmental triggers for autism.
Fifteen years ago, research focused on autism as a genetic condition. Now many experts believe the disorder is triggered by a combination of environmental and genetic factors.
About one in every 150 children is diagnosed with autism, according to estimates from the Centers for Disease Control and Prevention.
