Autism Spectrum Disorder: Incidence and Time Trends Over Two Decades in a Population-Based Birth Cohort

We retrospectively identified autism spectrum disorder (ASD) incident cases among 31,220 individuals in a population-based birth cohort based on signs and symptoms uniformly abstracted from medical and educational records. Inclusive and narrow research definitions of ASD (ASD-RI and ASD-RN, respectively) were explored, along with clinical diagnoses of ASD (ASD-C) obtained from the records. The incidence of ASD-RI, ASD-RN, and ASD-C increased...