Prevalence of autism in a United States population: The Brick Township, New Jersey, investigation

Objective. This study determined the prevalence of autism for a defined com munity, Brick Township, New Jersey, using current diagnostic and epidemiolo gic methods. Methods. The target population was children who were 3 to 10 years of age i n 1998, who were residents of Brick Township at any point during that year, and who had an autism spectrum disorder. Autism spectrum disorder was defi ned as autistic disorder, pervasive developmental disorder-not otherwise sp ecified (PDD-NOS), and Asperger disorder. The study used 4 sources for acti ve case finding: special education records, records from local clinicians p roviding diagnosis or treatment for developmental or behavioral disabilitie s, lists of children from community parent groups, and families who volunte ered for participation in the study in response to media attention. The aut ism diagnosis was verified (or ruled out) for 71% of the children through c linical assessment. The assessment included medical and developmental histo ry, physical and neurologic evaluation, assessment of intellectual and beha vioral functioning, and administration of the Autism Diagnostic Observation Schedule-Generic. Results. The prevalence of all autism spectrum disorders combined was 6.7 c ases per 1000 children. The prevalence for children whose condition met ful l diagnostic criteria for autistic disorder was 4.0 cases per 1000 children , and the prevalence for PDD-NOS and Asperger disorder was 2.7 cases per 10 00 children. Characteristics of children with autism in this study were sim ilar to those in previous studies of autism. Conclusions. The prevalence of autism in Brick Township seems to be higher than that in other studies, particularly studies conducted in the United St ates, but within the range of a few recent studies in smaller populations t hat used more thorough case-finding methods.