Substance Use in Individuals with Mild to Borderline Intellectual Disability: an Exploration of Rates and Risks in the Netherlands

Little is known about rates and risk factors of substance use (SU) in individuals with mild to borderline intellectual disabilities (MBID, IQ 50–85). This hinders targeted prevention and treatment. In this study we assessed SU rates and risk factors in individuals with MBID in 419 adults (63% male, average IQ = 66) in 16 Dutch disability services. Lifetime and current SU, SU picture recognition, knowledge, attitudes and modeling were assessed with the Substance use and misuse in Intellectual Disability - Questionnaire (SumID-Q). Lifetime licit SU (alcohol and tobacco) was 97%, lifetime illicit SU (predominantly cannabis) was 50%. Current users of tobacco (62%), alcohol (64%), and cannabis (15%) initiated SU at a younger age than those who desisted SU (ps < .001). Participants with mild ID and those with borderline ID did not differ in SU rates (ps .429–.812), or age at SU initiation (ps .221–.853). Current licit SU and lifetime illicit SU were related to male gender, younger age, and (for smoking and stimulant use) to lack of daytime activities. However, these factors did not contribute to multivariate models when recognition, knowledge, attitudes and modeling were added. The models correctly identified current SU in 84% (smoking) and 74% (drinking), and lifetime SU in 76% (cannabis) and 84% (stimulants) of the participants. As almost all participants reported lifetime use of licit, and about half reported lifetime illicit substance use, systematic screening for substance use, and development of preventative and treatment interventions targeted to this group are needed.