Two community-based cohorts of children with autism spectrum disorder, examined using similar assessment protocols, were pooled (n=301) and subdivided according to history of regression. Those with regression (n=62), 20.5% of the combined cohort, were contrasted with those without regression (n=241) at first assessment (age range 19–60 months) and at 2-year follow-up on a range of measures. The regression group was significantly more functionally impaired, with regard to intellectual function (p<.001), language development (p<.001), and to severity of autism (p<.01) at both T1 and T2. Only 14 (23.3%) had a clearly identified underlying etiology [24 (18.6%) in the non-regressive group]. There were no significant differences between those who had regressed ‘from normal’ and those who had regressed ‘from low’ functioning.
- Regressive autism
- Non-regressive autism
- Intellectual developmental disorder
- Developmental language disorder