Equity effects of parenting interventions for child conduct problems: a pan-European individual participant data meta-analysis.

Childhood conduct problems are a costly public health problem and are five times more common in socially disadvantaged groups than they are in advantaged groups. Untreated, conduct problems have a poor prognosis, with increasing gaps between socioeconomic groups, and high rates of subsequent criminality. Incredible Years is a high quality parenting programme for reducing conduct problems and is widely disseminated in Europe. Many trials have shown Incredible Years to be effective but the potential effects of parenting interventions on social inequality are unknown. Some behavioural interventions (eg, smoking cessation programmes), although beneficial overall, can widen inequality gaps. Because single trials and aggregate-level meta-analyses are ill equipped for examining differential intervention (moderator) effects, we pooled individual-level trial data to assess the effects of Incredible Years on social equity.