This study aimed to provide an autism spectrum disorder (ASD) prevalence update from parent and teacher report using the Longitudinal Study of Australian Children (LSAC). The LSAC is a prospective cohort study of Australian children representative of the population with two cohorts: Kinder (birth year 1999/2000) and Birth cohort (birth year 2003/2004). Children in the Birth and Kinder cohort with parent- and teacher-reported ASD prevalence were compared to children without ASD. There were N = 3,381 (66%) responding in the Birth cohort at age 12 and N = 3,089 (62%) for the Kinder cohort at age 16. Quality of life was measured by the Pediatric Quality of Life Inventory, and emotional/behavior problems using the Strengths and Difficulties Questionnaire. Parent-reported ASD prevalence increased to 4.36% [95% CI 3.56-5.19] at age 12-13 years in the Birth cohort and 2.60% [95% CI 2.07-3.31] in the Kinder cohort. Kinder cohort ASD children had more parent- and teacher-reported social problems, and lower parent-reported social and psychosocial quality of life. As expected, parent-reported ASD prevalence continued to rise. The higher prevalence in the Birth cohort may relate to milder cases of ASD being diagnosed. LAY SUMMARY: Parent-reported ASD prevalence in 2016 in 12-year-old children from the Birth cohort of the Longitudinal Study of Australian Children was 4.4%, and higher than the 2.6% in the earlier born Kinder cohort. The Birth cohort had a milder presentation with fewer social, emotional, and behavioral problems than the Kinder cohort. Milder cases of ASD are being diagnosed in Australia resulting in one of the highest reported prevalence rates in the world. © 2020 International Society for Autism Research, Wiley Periodicals, Inc.
© 2020 International Society for Autism Research, Wiley Periodicals, Inc.

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