Increased rainfall, or something linked to it, may be connected to the development of autism, according to a research in Archives of Pediatrics and Adolescent Medicinea as quoted by media reports Tuesday.

The rainfall autism theory is based on child health and weather records from three US states, but has been greeted cautiously by a UK research charity.

The researchers calculated average annual rainfall for California, Oregon and Washington State between 1987 and 1999, then looked at autism prevalence rates in the children growing up during this period.

The study found autism rates were higher among children whose states experienced higher rainfall in their first three years. The rising rates of autism - up, by some measures, from one in 2,500 to one in 150, has been attributed mainly to improvements in the way doctors are able to recognize the disease, some scientists argued.
However, researchers from Cornell University disagreed, saying this should not exclude a factor which may be independently increasing the number of children growing up with the condition.

They found that rates could be linked to that amount of precipitation in their state between these dates.

They said: "Autism prevalence was higher for birth cohorts that experienced relatively heavy precipitation when they were younger than three years."

They also made it clear that none of these was more than a theory, and called for further research to see if the link was a real one.