Substance use disorder among people with intellectual and developmental disabilities: a narrative review

<i>Background:</i> Research on substance use disorder (SUD) and intellectual and developmental disabilities (IDD) is limited. Literature suggests people with IDD are less likely to use substances; however, they are more susceptible to SUD if they do.<i>Objectives:</i> To better understand the relationship between IDD and SUD and identify best practices to improve adherence to treatment and health outcomes.<i>Methods:</i> A narrative review of English peer-reviewed sources published between January 2000-May 15, 2025 was conducted using CINAHL, Pubmed, Scopus, Web of Science, Academic Search Complete, and PsychINFO. Measures of interest included co-occurrence of SUD and IDD, and risk factors, treatment options, and barriers to receiving or adhering to treatment for adults with IDD and SUD.<i>Results:</i> Prevalence of substance use is lower in adults with IDD than without IDD. Adults with IDD and SUD are most commonly encountered in outpatient mental health settings. Cannabis, alcohol, and cocaine are the most frequent substances used by individuals with IDD. Risk factors for IDD and SUD include male gender, family history of SUD, exposure to peers who use substances, psychiatric comorbidities, and mild/borderline IDD as compared to no IDD. Approximately 42-54% of individuals with IDD and SUD have co-occurring psychiatric disorders. Staff who provide SUD treatment are not trained to work with IDD.<i>Conclusions:</i> Outcomes for individuals with IDD and SUD would improve with development of SUD and IDD specific training for providers and treatment protocols that account for risk factors such as peer relationships, family history of SUD, and co-morbid mental health diagnoses.