A comparison study of autism spectrum disorder referrals 1997 and 1989.

A number of overseas studies have indicated an increase in the prevalence of Autism Spectrum Disorder (ASD). In the Australian Capital Territory, information (number, age, sex, final diagnosis) was gathered on all children referred for suspected ASD to Child and Adolescent Mental Health Service during 1997, and the findings were compared with those from a similar study in 1989. It was found that (1) there was a 200% increase in positive diagnoses of ASD in 1997 despite a 0.5% decrease in population, (2) there was a wider age range in the 1997 cohort, (3) there was a 26% increase in milder cases in 1997, and (4) the ratio of boys to girls decreased from 8:1 in 1989 to 3.5:1 in 1997. These findings are compared with those overseas, and questions are raised for further exploration.