A riddle wrapped in an enigma

As Professor Eric Courchesne flew home to California this week after his speech to the inaugural World Autism Congress in Melbourne, parents were digging out their children's growth charts and foraging for the tape-measure.

The UCLA professor had been the star at the gathering of 1500 scientists, doctors, autism case workers and parents, all absorbed in finding causes and treatments for the mystery disorder. He came promising a "breakthrough announcement", and he delivered. He revealed his discovery that babies who develop autism often have an abnormal brain growth-spurt between four months and one year. The finding could be highly significant in early detection and, maybe, prevention.

His research was aimed at giving scientists another piece of the puzzle, but inevitably he also delivered parents one more thing to be afraid of. Within hours the phones at autism support groups and associations around Australia were running hot.

In the 60 years since it was identified and defined, the mystery of just what causes autism has confounded researchers and preoccupied parents. It is largely accepted that sufferers have a genetic predisposition, but what factors it may take to trigger full-blown symptoms - which impair to varying degrees social, communication, motor and other behavioral skills - still elude the increasingly large community touched by autism.

The search has become more urgent in the past five years as the incidence of autism, which most often strikes boys, has apparently doubled from roughly one in 1000 to one in 500. In pockets such as the Barwon region of Victoria, it is as common as one in 200.