Diagnostic change and the increased prevalence of autism

A wide spectrum of studies conducted in numerous locales suggest that the measured prevalence of autism, a condition characterized by impairments in social interaction and communication, has increased markedly over the past 40 years. Consistent with previous studies, data from the California Department of Developmental Services (DDS) show that between 1987 and 2003 the number of autism cases handled by the California DDS increased by 634%. The general consensus is that these increases are striking. Equally striking is the absence of consensus regarding the degree to which changes in diagnostic standards, practice and procedures, and/or diagnostic substitution have contributed to increased prevalence rates.