Design: A systematic review using electronic searches of PsycINFO, PsycTESTS, EMBASE, MEDLINE, CINAHL, ERIC, ASSIA, Science Citation Index, Social Science Citation Index and CENTRAL was conducted to identify eligible intervention studies. Study selection, data extraction and quality appraisal were performed by two independent reviewers.
Participants: Study samples included at least 70% children and/or adults with severe or profound intellectual disabilities or reported the outcomes of this subpopulation separate from participants with other levels of intellectual disabilities.
Interventions: Eligible intervention studies evaluated a psychological or pharmacological intervention using a control condition or pre-post design.
Outcomes: Symptom severity, frequency or other quantitative dimension (e.g., impact), as assessed with standardised measures of mental health problems.
Results: We retrieved 41 232 records, reviewed 573 full-text articles and identified five studies eligible for inclusion: three studies evaluating pharmacological interventions, and two studies evaluating psychological interventions. Study designs ranged from double-blind placebo controlled crossover trials to single-case experimental reversal designs. Quality appraisals of this very limited literature base revealed good experimental control, poor reporting standards and a lack of follow-up data.
Conclusions: Mental ill health requires vigorous treatment, yet the current evidence base is too limited to identify with precision effective treatments specifically for children or adults with severe and profound intellectual disabilities. Clinicians therefore must work on the basis of general population evidence, while researchers work to generate more precise evidence for people with severe and profound intellectual disabilities.