A new study sheds more light on the question of what is causing the recent increase in the rate of diagnosis of autism. Professor Dorothy Bishop from the University of Oxford studied adults who were diagnosed in 1980 with a developmental language disorder. She asked the question – if these people were subjected to current diagnostic criteria for autism, how many of them would be diagnosed today as having autism? She found that 25% of them would. (Bishop 2008)

Among the many great mysteries of autism is this: Where are all the adults with the disorder? In California, for instance, about 80% of people identified as having an autism spectrum disorder (ASD) are 18 or under. Studies by the Centers for Disease Control and Protection (CDC) indicate that about 1 in 150 children in the U.S. have autism, but despite the fact that autism is by definition a lifelong condition, the agency doesn't have any numbers for adults. Neither has anyone else. Until now.

On Sept. 22, England's National Health Service (NHS) released the first study of autism in the general adult population. The findings confirm the intuitive assumption: that ASD is just as common in adults as it is in children. Researchers at the University of Leicester, working with the NHS Information Center found that roughly 1 in 100 adults are on the spectrum — the same rate found for children in England, Japan, Canada and, for that matter, New Jersey.