Scientists baffled by increase in autism

The dramatic increase in the number of children diagnosed with autism over the last five years could be due to environmental factors, a new study suggests.

Researchers from the University of California found that a 287 per cent rise in the condition there could not be explained by increased aware- ness or better methods of diagnosis, as first suspected.

Instead, scientists believe children may be born with a genetic predisposition to autism which is triggered by an unknown external factor. Autism affects a person's ability to communicate and form relationships with other people or to relate to the world.

Dr Fiona Scott of the Autism Research Centre at Cambridge University said that in this country rates had increased from four in 10,000 five years ago to around one in 100 now. "The California study is the first to look at questions of misdiagnosis, migration or increased awareness as explanations for the rise," Dr Scott said. "Some scientists are now thinking that we could be born with a genetic susceptibility that can be triggered. Nobody knows what that trigger could be." She added: "We need to get a clearer picture of what is going on because we don't know for sure what the rates of autism are."

Dr Robert Byrd, of the University of California, who led the research, said: "Autism is on the rise and we do not know why. The results of this study are sobering."

The study will now be replicated with a much larger sample size.