A multilevel meta-analysis of single-case and small-n research on interventions for reducing challenging behavior in persons with intellectual disabilities

► Effectiveness articles of interventions on challenging behavior (CB) in persons with ID are studied. ► Single-case data are combined using a hierarchical linear model meta-analysis. ► A large and statistically significant overall treatment effect is found, but the effect varies over participants and studies. ► CB topographies and intervention components significantly moderate treatment effects.