LAUSR

Parenting interventions are an effective strategy to reduce children’s conduct problems. For some families, that is, not all families benefit equally. Individual trials tend to be underpowered and often lack variability to differentiate between families how benefit less or more. Integrating individual family level data across trials, we aimed to provide more conclusive results about often presumed key family (parental education and ethnic background) and child characteristics (problem severity, ADHD symptoms and emotional problems) as putative moderators of parenting intervention effects. We included data from 786 families (452 intervention; 334 control) from all four trials on the Incredible Years parenting intervention in The Netherlands (three randomized; one matched control). Children ranged between 2 and 10 years (M = 5.79; SD = 1.66). Of the families, 31% had a lower educational level and 29% had an ethnic minority background. Using multilevel regression, we tested whether each of the putative moderators affected intervention effects. Incredible Years reduced children’s conduct problems (d = − .34). There were no differential effects by families’ educational or ethnic background, or by children’s level of ADHD symptoms. Children with more severe conduct problems and those with more emotional problems benefited more. Post hoc sensitivity analyses showed that for the two trials with longer-term data, moderation effects disappeared at 4 or 12 months follow-up. Often assumed moderators have some, but limited abilities to explain who benefits from parenting interventions. This suggests the need for studying theoretically more precise moderators in prevention research, other than relatively static family characteristics alone.