Autism is a brain development disorder that occurs in children, generally, before turning 3 and is characterized by impaired social interaction or communication, repetitive behavior or even complete mental retardation.

Scientists don’t know what exactly causes autism and many theories have been forwarded, linking autism to severe genetic mutation, or theories claiming that the changes occur while the fetus is still in the mother’s womb and most recently, that the weather might have something to do with autism.

Scientists have analyzed cases of children who suffer from autism from Oregon, California and Washington and have compared the data with the precipitation reports in these states from 1987 to 1999. The results indicate that more children with autism have been reported in areas with more rainfall.

The theory is only backed up by the raw data as the scientists can’t really explain how dry or wet climates could directly affect a child in such a way. Among the possible explanations, scientists have said that maybe because in a rainy climate a child spends more time indoors, not being sufficiently exposed to fresh air and to sunlight, which provides Vitamin D in the body. Other explanations involve chemicals that are brought down by rain from the upper atmospheres, chemicals that might have a role to play in the development of this disorder.

On the other hand, reports say that the number of children suffering from autism has increased overall, both in dry or wet climates. All in all, the U.S. Centers for Disease Control and Prevention have started a long-term study on the causes of autism, in order to find better treatments and apply preventive measures.