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

Objectives: This meta-analysis examined the effectiveness of psychosocial interventions for youth with mild intellectual disabilities or borderline intellectual functioning (MID-BIF) and externalising problems. 

Methods: We assessed 2221 studies for eligibility and included seven studies containing 14 effect sizes. We used a multilevel modelling approach to analyse the data and calculated two different types of effect sizes: one for controlled trials and one for intervention pre-test to post-test effects (across all studies). 

Results: Both controlled trial effect sizes (g = 0.49) and pre-test to post-test effect sizes were significant (g = 0.53). We were unable to detect heterogeneity of effects because of the small number of eligible studies. The risk of bias was generally high. 

Discussion: Results suggest that psychosocial interventions decrease externalising problems among youth with MID-BIF. Effect sizes appear similar to those for youth without MID-BIF. We discuss recommendations for how the field can move forward.