The mediating role of substance use motives in the relationship between personality dimensions and alcohol and drug use in adolescents and young adults with mild intellectual disabilities.

Adolescents and young adults with mild intellectual disabilities or borderline intellectual functioning (MID-BIF) are a high-risk group for developing substance use disorders. The aim of this study was to gain a better understanding of the mechanisms that underlie substance use in this particular population. We tested the mediating role of substance use motives in the relationship between personality dimensions and substance use-related outcomes. Self-reported data on substance use risk personality dimensions (i.e., sensation seeking, impulsivity, anxiety sensitivity, and negative thinking), substance use motives (i.e., social, enhancement, coping, and conformity motives), and substance use were obtained from 163 individuals with MID-BIF (mean age 18.9 years). Results show that coping motives played a main role in the associations between personality dimensions and substance use in adolescents and young adults with MID-BIF, with significant relationships between impulsivity and negative thinking and severity of alcohol use or drug use via coping motives. Moreover, findings indicated a relatively high risk for several substance use motives and associated substance use (disorder) in individuals high on impulsivity. Results show significant relationships between impulsivity and severity of alcohol use or drug use via social, enhancement, and coping motives. No mediating associations were found for conformity motives, nor did we find any mediation associations in individuals with high levels of anxiety sensitivity. These insights provide the possibility of tailoring interventions to specific motives that underlie substance use in different types of users with MID-BIF based on personality dimensions.