Effectiveness of the Incredible Years parent training to modify disruptive and prosocial child behavior: a meta-analytic review

Meta-analysis of 50 studies of the Incredible Years parent program. Reduced disruptive child behavior with a mean effect of d=0.27 across informants (larger, ~d=0.50, in treatment vs. prevention samples). Initial severity of child behavior was the strongest predictor: children with more problems benefited most.