a1 Washington University School of Medicine
Recent research has suggested that autistic social impairment (ASI) is continuously distributed in nature and that subtle autistic-like social impairments aggregate in the family members of children with pervasive developmental disorders (PDDs). This study examined the longitudinal course of quantitatively characterized ASI in 3- to 18-year-old boys with and without PDD. We obtained assessments of 95 epidemiologically ascertained male–male twin pairs and a clinical sample of 95 affected children using the Social Responsiveness Scale (SRS), at two time points, spaced 1–5 years apart. Longitudinal course was examined as a function of age, familial loading for PDD, and autistic severity at baseline. Interindividual variation in SRS scores was highly preserved over time, with test–retest correlation of 0.90 for the entire sample. SRS scores exhibited modest general improvement over the study period; individual trajectories varied as a function of severity at baseline and were highly familial. Quantitative measurements of ASI reflect heritable traitlike characteristics. Such measurements can serve as reliable indices of phenotypic severity for genetic and neurobiologic studies, and have potential utility for ascertaining incremental response to intervention.
c1 Address correspondence and reprint requests to: John N. Constantino, Washington University School of Medicine, 660 South Euclid Avenue, Campus Box 8134, St. Louis, MO 63110; E-mail: firstname.lastname@example.org.
This work was supported by Grant HD042541 from the National Institute of Child Health and Human Development (to J.N.C.). We gratefully acknowledge the parents and families participating in the Washington University Social Developmental Studies Program and the Missouri Family Registry for their ongoing dedication to scientific research. This work is dedicated to the memory and continuing legacy of the late Richard D. Todd, PhD, MD, a pioneer in child psychiatric genetics and this manuscript's senior author (for whom it is published posthumously).