Psychological Need Satisfaction and Simultaneous Alcohol and Marijuana Use: A Moderated Mediation Model of Expectancies and Motives

<b><i>Background</i></b>: Prior work suggests psychological need satisfaction (PNS) may protect against single-substance alcohol and marijuana use, yet little is known about its association with simultaneous alcohol and marijuana (SAM) use. This study aims to address this gap by examining the link between PNS and SAM use in college students. Further, to better explain the conditions under which PNS associates with SAM use, we also explore SAM use motives as a potential mechanism through which PNS associates with SAM use, and investigate whether this relationship is moderated by positive expectancies about SAM use (i.e., first-stage moderated mediation). <b><i>Methods</i></b>: Participants were 822 college students from six universities who reported past-month SAM use. The sample was predominantly White, non-Hispanic (62.9%), female (70.2%), with a mean age of 19.44 (<i>SD</i> = 1.98) years. <b><i>Results</i></b>: Calm/coping and social motives mediated the association between PNS and SAM use, such that students with lower PNS reported higher levels of these motives, which were in turn associated with greater SAM use. The indirect effect of PNS on SAM use through calm/coping motives, but not social motives, was stronger among students with higher levels of positive expectancies for SAM use, compared to those with lower or average positive expectancies. <b><i>Consclusion</i></b>: These findings suggest that students with lower PNS and higher positive SAM expectancies may be at greater risk of engaging in SAM use, especially for relaxation or coping reasons. Overall, the results highlight the importance of addressing unmet psychological needs and positive expectancies in efforts to reduce SAM use among college students.