BACKGROUND: There is a lack of available evidence in relation to the effectiveness of interventions for adults with mild to moderate intellectual disability and mental health problems.

AIMS: To evaluate the efficacy of interventions for adults with mild to moderate intellectual disabilities and co-occurring mental health problems.

METHOD: An electronic literature search of the databases Medline, EMBASE, PsycINFO and EBM Reviews aimed at identifying randomised controlled trials (RCTs) and controlled trials testing any type of intervention (psychotherapy, biological or system level) for people with mild to moderate intellectual disabilities (IQ score 35-69) targeting comorbid mental health problems. Additionally a meta-analysis was conducted.

RESULTS: Twelve studies met the inclusion criteria. No significant effect was found for the predefined outcome domains behavioural problems, depression, anxiety, quality of life and functioning. The effect size for depression (d = 0.49) was moderate but non-significant. Quality of studies was moderate and heterogeneity was high.

CONCLUSIONS: There is no compelling evidence supporting interventions aiming at improving mental health problems in people with mild to moderate intellectual disability. The number of available trials is too low for definite conclusions. Some interventions are promising and should be evaluated further in larger and more rigorous trials.