Abstract
Given the growing number of fatalities associated with the use of multiple types of drugs, there is an urgent need for a tool that allows clinicians and researchers to quickly assess diverse reasons for substance use. Here, we sought to validate the Motivational Inventory Underlying Substance Engagement (MI-USE), a new measure that assesses motivations for use across different types of substances. Participants were 538 adults ages 18-60 (48% women) who reported substance use problems and past-year drug or alcohol use. Analyses were conducted to discover and validate the factor structure of the MI-USE and evaluate its construct validity. A 30-item model best fit the MI-USE, with one General Factor capturing overall motivation to engage in substance use and eight motive-specific factors that indexed unique motivations for substance use: Emotional Coping (relief from unpleasant emotions), Pleasure-Seeking (feel pleasurable or exciting emotions and sensations), Dependence Severity (avoid withdrawal and cravings), Expansion (enhance self-insight and spirituality), Social Coping (increase confidence and attractiveness), Advantage (gain a physical or mental advantage), Physical Coping (relief from unpleasant bodily sensations), and Sleep (mitigate sleep problems). Evaluation of the measure's construct validity and internal consistency support the chosen model and interpretation of the motive-specific factors. Results provide initial validation of the MI-USE as a reliable and valid tool for assessing diverse substance use motivations. It improves upon existing measures by allowing clinicians and researchers to simultaneously evaluate motivations for multiple forms of substance use, which facilitates personalized treatment planning and research on polysubstance use.