Promoting self-determination of persons with severe or profound intellectual disabilities: a systematic review and meta-analysis.

People with severe or profound intellectual disabilities (IDs) are believed to experience low levels of self-determination, which negatively affects their quality of life. This systematic review describes existing interventions aimed to support self-determination or components thereof and synthesises evidence on the interventions' effects. Eight databases were searched, turning in 76 articles for the final inclusion. The studies included 631 people with severe or profound IDs of whom 81% had multiple disabilities. The studies had quantitative (k = 63), qualitative (k = 7) and mixed study designs (k = 6). Sample sizes ranged from 1 to 95 and a study quality index ranged from 40% to 100%. While many studies included several self-determination components and intervention elements, overall, 53 studies focused on the self-determination components choice making, independence and problem solving. Other studies included increased assistance (k = 14); engagement in meaningful activities and relationships (k = 10); community and societal participation (k = 5); supporting the basic psychological needs autonomy, competence and relatedness (k = 4); individuality and dignity (k = 3); supportive decision-making (k = 2); self-advocacy (k = 2); and motivation (k = 1). Intervention elements included technology (k = 33); multiple-component training packages, goal setting, empowerment tactics and applied behaviour principles (k = 17); training of caretakers (k = 17); changes in policies and living arrangements (k = 9); supporter responsiveness (k = 1); drama therapy and storytelling (k = 1); electrical wheelchair training (k = 1); joint painting procedure (k = 1); youth advocacy project (k = 1); and multiliteracies training (k = 1). Reflecting the heterogeneity of the field, only four studies tested a similar intervention for this population and were eligible for the meta-analysis, which combined showed a small effect size of 2.69. Further research is needed to explore relationships between individuals with severe or profound IDs and their relatives and health care professionals and create supportive environments that meet their basic psychological needs.