The estimated prevalence of autism spectrum disorder (ASD) is higher than previously recorded, according to the Autism and Developmental Disabilities Monitoring (ADDM) Network. Between 2000- 2014, the prevalence increased from 6.7 to 16.8 per 1,000 children, a jump of about 150%.
Autism and Developmental Disabilities Monitoring is a surveillance system that estimates the prevalence of autism spectrum disorder among children aged 8 years who live within 11 sites (Arizona, Arkansas, Colorado, Georgia, Maryland, Minnesota, Missouri, New Jersey, North Carolina, Tennessee, and Wisconsin). Autism and Developmental Disabilities Monitoring does not depend on family or practitioner reporting to determine ASD case status. Instead, staff conduct surveillance in a 2-phase process: reviewing children’s evaluation records from data sources in the community (including “developmental assessments completed by a wide range of health and education providers”), and compiling them into a comprehensive record that is then reviewed by ≤ 1 experienced clinicians.
Certain characteristics remained similar in 2014 compared with earlier surveillance years, ADDM researchers say. For instance, the median age of earliest known ASD diagnosis was 52 months in 2014, compared with close to 53 months in previous years.
However, male-to-female prevalence changed slightly, from 4.5:1 to 4:1, driven by a greater relative increase in ASD prevalence among girls since 2012. Autism and Developmental Disabilities Monitoring also points to a trend that begun in 2002 of a decrease in the ratios of white to black children and white to Hispanic children. Historically, ADDM researchers say, estimates have been 20% to 30% higher among white children compared with black children and 50% to 70% higher compared with Hispanic children. In 2014, those numbers dropped to 7% (the lowest difference ever observed by ADDM) and 22%, respectively.
Implementation of the new DSM-5 case definition had little effect on the overall number of children identified with ASD in 2014, ADDM researchers say.