Effectiveness of Psychosocial Interventions for Youth With Mild Intellectual Disabilities or Borderline Intellectual Functioning and Externalising Problems: A Multilevel Meta-Analysis.

Only seven unique studies with 421 participants were included, so the evidence base is small. Five of the seven studies had a high risk of bias, and two had some concerns. Common bias problems were inadequate randomisation, completers-only analysis, missing outcome data and subjective outcome measures. Funnel plot asymmetry suggested smaller studies reported larger positive effects, so the overall effect may be inflated. The review had insufficient power to detect moderators or heterogeneity, so it cannot say which patients or intervention features work best. Only two studies reported follow-up, so it is unclear whether effects lasted. English-language studies only and single-case designs were excluded, so relevant studies may have been missed. Uncontrolled pre-test to post-test studies were included, which can inflate effects, although controlled-trial and pre-post estimates were similar.

The authors declared no conflicts of interest.

Do not conclude that psychosocial interventions are proven effective for youth with mild intellectual disability or borderline intellectual functioning. The review found positive effects, but only seven studies were included, most had high risk of bias, and smaller studies reported larger positive effects.