Abstract
In this second of two primary papers, we examined two pre-intervention characteristics that might describe for whom a parent-implemented intervention, "Improving Parents As Communication Teachers," worked. Investigators randomized 97 high-risk siblings and their primary parent to either the Improving Parents As Communication Teachers or control group, used intent-to-treat analysis, and used assessors and coders who were blinded to group assignment. We predicted that a combined risk score (incorporating young siblings' sex, multiplex status, and behavioral risk) would describe the subgroup for whom Improving Parents As Communication Teachers affected the targeted skills related to reducing communication challenges. We also predicted that pre-intervention level of parents' depressive symptoms would describe the parents whose parenting stress and effectiveness as parents would be improved by learning to use Improving Parents As Communication Teachers. In girls with only one older sibling with autism spectrum disorder and who scored at low risk on an autism spectrum disorder screen, parental receipt of Improving Parents As Communication Teachers training had an indirect effect on children's expressive language ability or autism spectrum disorder diagnosis through earlier effects on high-risk siblings' intentional communication or expressive vocabulary. We did not confirm our prediction regarding Improving Parents As Communication Teachers' effect on parenting-related stress or sense of parenting effectiveness.