Developmental regression among children with autism spectrum disorder: Onset, duration, and effects on functional outcomes

• Regression in ASD was examined in the largest sample to date using the ADI-R.
• A supplemental interview successfully captured more parent-reported regressions.
• Effects of regression on cognitive and adaptive-functioning outcomes were assessed.
• Any degree of language loss was associated with poorer outcomes.
• Only full other-skill losses were associated with poorer outcomes.

Studies using varied methods report that developmental regression occurs in a sizeable proportion of children with autism spectrum disorder (ASD). Findings are equivocal as to whether regression is associated with poorer cognitive and adaptive functioning. This study examined retrospective parent report in 2105 Simons Simplex Collection participants with ASD. Children were classified as having “full” or “subthreshold” losses on language and/or other skills using items from the Autism Diagnostic Interview-Revised (ADI-R) and a supplemental interview to capture more subtle regressions. Overall, 36.9% of children had some type of regression (27.8% language, 27.0% other-skill loss), with the supplemental interview capturing 11.7% of losses that would have been missed using the ADI-R alone. This figure is consistent with previous parent-report studies but lower than clinician-observed rates in prospective investigations. Early language losses—either full or subthreshold—and full other-skill losses appear to be associated with more deleterious outcomes by middle childhood. Findings may signify the need for more immediate and/or intense therapies for children who have even minor skill losses, particularly in language skills. Results further demonstrate the utility of an expanded set of additional queries with slightly modified criteria to capture such early, subtle losses.