Illicit drug use and prescription drug misuse among young adult medical marijuana patients and non-patient users in Los Angeles

Introduction: Drug use, including marijuana use, illicit drug use and prescription drug misuse, and mental health comorbidity among young adults are pressing public health concerns. Young adults comprise a significant proportion of the total population of medical marijuana patients (MMP). Little is known about the role of MMP status, medicinal orientation towards marijuana use, other marijuana practices, mental health, life events and contextual factors in the patterns of illicit drug use and prescription drug misuse among young adult MMP and non-patient users (NPU). Methods: The current study utilized a mixed-methods design to investigate the relationships between baseline rates and longitudinal trajectories of illicit drug use/prescription drug misuse and marijuana practices/mental health, and to explore the role of life events/contextual factors in the patterns of illicit drug use and prescription drug misuse in a sample of 210 MMP and 156 NPU aged 18-26 at baseline (n=366), recruited in Los Angeles in 2014-15. A subsample of 40 MMP and 22 NPU was selected for qualitative interviews. Results: Findings from the cross-sectional quantitative analysis indicated an association between use of alternative marijuana forms and illicit drug use/prescription drug misuse, with medicinal orientation towards marijuana use (but not MMP status) being protective against illicit drug use. Neither type of drug use was associated with frequency of marijuana use. Findings from the longitudinal quantitative analysis identified two-trajectory (high vs low) solutions for both types of drug use. High use trajectories were associated with the use of alternative marijuana forms, higher anxiety and depression symptoms, and higher drug use severity scores. Neither trajectory type was associated with MMP status, while medicinal orientation towards marijuana use was negatively associated with high illicit drug use trajectory. Only high prescription drug misuse trajectory was associated with higher frequency of marijuana use. Findings from the qualitative analysis revealed three patterns of illicit and prescription drug use/misuse: regular/problematic, recreational/occasional and never use. The majority of regular/problematic users experienced impactful traumatic events/chronic stressful contextual factors, and almost all of them used marijuana to deal with after-effects of use of other drugs. Some recreational/occasional and few never users experienced impactful traumatic events, and the majority self-medicated with marijuana for emotional pain as aftermath of those events. Family history of substance abuse and acceptance of marijuana use by adult family members for some recreational/occasional and some never users could serve as protective factors from initiation/escalation of other drug use. Conclusion: Medicinal orientation towards marijuana use (but not MMP status) was negatively associated with illicit drug use. Use of alternative marijuana forms (but not frequency of marijuana use) had a strong and consistent association with both illicit drug use and prescription drug misuse. Additionally, both types of drug use were associated with worse mental health outcomes. Finally, life events/contextual factors played an important role in initiation/escalation and reduction/cessation of other drug use among regular/problematic users. Use of marijuana helped to cope with the after effects of other drugs among regular/problematic users, while marijuana was used as a self-medication for emotional pain by those recreational/occasional and never users who experienced impactful traumatic events. Overall, the results from cross-sectional, longitudinal, and qualitative analyses showed no relationship between MMP status and illicit/prescription drug use, while we found a strong and consistent protective effect of medicinal motivations for marijuana use.