Using Momentary Sampling to Identify Consequences of Simultaneous Alcohol and Marijuana Use in Young Adults

Introduction: Cannabis is the most widely used illicit drug and rates of hazardous use, and cannabis use disorders (CUDs), have continued to rise in recent years. Young adults have the highest rates of cannabis use, with past month cannabis use rates increasing significantly in this age group over the last 5 years. The vast majority of young adults also use alcohol, suggesting there is an increasingly prevalent sub-group of young adults who are using both substances simultaneously. However, the risks associated with simultaneous alcohol and marijuana (SAM) use have received a more limited focus in prior research. The prior research findings on SAM use have identified associations with a broad range of hazardous consequences, including risk behaviors, mental health and physical health outcomes. Yet despite the increasing prevalence of cannabis and alcohol use, very little research has examined the real world effects of SAM use on moment-to-moment changes in psychological states and behaviors. Ecological momentary assessment (EMA) and related intensive repeated within-subjects methods offer the opportunity to expand upon prior cross-sectional research to examine complex directional and causal relationships in SAM use among young adults.

Methods: Young adults (18-30 years old) who engaged in regular (once weekly) or recreational (monthly) cannabis use participated in a 21-day smartphone-based EMA protocol in which they reported on all substance use, including alcohol and cannabis consumption, mental, physical health outcomes over the course of each day. Lagged use and outcomes were analyzed using multi-level models in order to examine sequelae of SAM use. Gender was also examined as a moderator of within-person processes in SAM effects.

Results: SAM use was associated with diminished mental and physical health at the time of use, suggesting motives for use of SAM may be driven by momentary psychological and physical states. Consequences of SAM use vary by gender, which may be indicative of different pathways for prevention and intervention.

Conclusions: These findings expend prior research by looking beyond generalizations of co-use to specific within-person processes of risk associated with instances of SAM. By clarifying the within-person process by which SAM use effects maladaptive outcomes, and the between-person processes, such as gender, that may moderate these outcomes, better prevention and intervention targets can be developed to target high-risk groups of cannabis and alcohol users.