Abstract
This article describes the symptoms of autism spectrum disorders (ASD) manifested by 405 individuals between the ages of 10 and 53 years, all of whom had an ASD diagnosis. Data were collected using the Autism Diagnostic Interview–Revised (ADI-R) to assess the pattern of autism symptoms in adolescence and adulthood. Findings include that although virtually all sample members met the criteria for Autistic Disorder earlier in their childhood, just over half (54.8%) would have met autism criteria if current scores were used to complete the diagnostic algorithm; that adolescents were more likely to improve in the Reciprocal Social Interaction domain than the adults, whereas the adults were more likely to improve in the Restricted, Repetitive Behaviors and Interests domain, and there were no differences in severity of symptoms between cohorts in the Communication domain; and that individual symptoms showed unique trajectories, with greatest symptom abatement between lifetime and current ADI-R ratings for speaking in at least three-word phrases and the least symptom improvement for having friendships. Findings were interpreted in the context of life course development, reformulations of diagnostic criteria, and changing service contexts for individuals with autism spectrum disorders.