Measuring autistic traits: heritability, reliability and validity of the Social and Communication Disorders Checklist

BACKGROUND: Autistic traits are widely distributed in the general population, but the boundaries of the autistic spectrum are unclear. Whole-population surveys of unselected samples of children are hampered by the lack of appropriate screening instruments. AIMS: To assess whether the Social and Communication Disorders Checklist (SCDC) fulfils the need for a sensitive measure of autistic traits, which can be completed in a few minutes and which measures heritable characteristics in both males and females. METHOD: A12-item scale, the SCDC, was completed by three independent samples drawn from a twin register, a group with Turner syndrome and children with a diagnosis of autistic-spectrum disorder attending clinics. The data were used to establish the heritability, reliability and validity of the checklist. RESULTS: Traits measured by the SCDC were highly heritable in both genders (0.74). Internal consistency was excellent (0.93) and test - retest reliability high (0.81). Discriminant validity between pervasive developmental disorder and other clinical groups was good, discrimination from non-clinical samples was better; sensitivity (0.90), specificity (0.69). CONCLUSIONS: The SCDC is a unique and efficient first-level screening questionnaire for autistic traits.