Social engagement with parents in 11-month-old siblings at high and low genetic risk for autism spectrum disorder.

Infant siblings of children with an autism spectrum disorder are at heightened genetic risk to develop autism spectrum disorder. We observed high risk (n = 35) and low risk (n = 27) infants at 11 months during free play with a parent. Children were assessed for autism spectrum disorder in toddlerhood. High-risk infants with a later diagnosis (n = 10) were less socially engaged with their parents than were low-risk infants. Parent behavior during play did not vary by group. Within the high-risk group, ratings of social reciprocity at 11 months predicted Autism Diagnostic Observation Schedule severity scores at follow-up, suggesting that systematic observations of parent-infant play may be a useful addition to early assessments of emerging autism spectrum disorder.