CDC today reported that Autism disorders increased by 57 per cent in just four years.

Autism numbers reported in 2007 survey reported last October was similar to the new CDC estimate of autism obtained from analysis of child evaluation records in 11 states.

Boys were more affected by autism than girls. According to a research one in 70 boys were diagnosed with autism, compared with one in 315 girls.

According to CDC behavioral health scientist Catherine Rice, who is also the lead author of the CDC report admits that there was no single reason for autism increase.

Geraldine Dawson, PhD, chief science officer of advocacy group Autism Speaks said that 20 years ago prevalence of one in 5,000 children was being looked and now it was one in 100.

CDC today released the Rice report as special report of the Morbidity and Mortality Weekly Report.

Geri Dawson, chief science officer for the advocacy group Autism Speaks, said this report confirmed that children were being affected by autism quite early and also how many children were affected.

The CDC report however also found a slight improvement in children diagnosed with the disorder. The average age of diagnosis was 4.5 years which was a five-month improvement from 2002.

This new prevalence report does not deal with the causes of autism. The study has attracted the attention of researchers who are looking into environmental factors that may trigger autism.