Research Review: Mechanisms of change and between-family differences in parenting interventions for children with ADHD - an individual participant data meta-analysis.

Background: Understanding the mechanisms of change and between-family differences in behavioural parenting interventions for children with attention-deficit/hyperactivity disorder (ADHD) may help personalise interventions. Therefore, we examined whether improvements in parenting are associated with changes in child behaviour and functional outcomes, and how these associations vary based on parents' baseline parenting levels.

Methods: We collected individual participant data including 19 randomised controlled trials focusing on children with ADHD (n = 1,720). Immediate post-intervention measures of child ADHD and oppositional behaviour severity, reported by parents and functional impairment reported by either the parent or probably masked clinicians, were treated as outcomes. We estimated pathways from intervention (vs. control) to child outcomes, via immediate post-intervention parent reports of constructive parenting (e.g. praise), non-constructive parenting (e.g. physical punishment) and parent-child affection (e.g. warmth), while controlling for baseline values of both child outcomes and parenting levels. Baseline values of each parenting variable were used as moderators of the mediated pathways.

Results: Improvements in parenting behaviours and parent-child affection immediately following the intervention jointly explained concurrent improvements in children's ADHD severity, oppositional behaviour and functional impairment. Furthermore, when reversing the direction of the pathways, improvements in all child outcomes jointly explained improvements in each aspect of parenting. Improvements in non-constructive parenting and parent-child affection uniquely accounted for intervention effects on functional impairment, especially for families with higher baseline levels of non-constructive parenting.

Conclusions: Our findings might indicate that improvements in both the behavioural and affective aspects of parenting are associated with concurrent reductions in child behaviour problems and functional impairment. However, more research is necessary to explore the potential causal directionality between parenting and child outcomes. Nonetheless, supporting families with poorer parenting skills may be especially important, as reductions in non-constructive parenting in these families are linked to stronger treatment effects on child functional impairment.