Developmental trajectories of illicit drug use, prescription drug misuse and cannabis practices among young adult cannabis users in Los Angeles.

<bold>Introduction and Aims: </bold>Young adults have the highest rates of drug use and contribute significantly to the growing population of medical cannabis patients (MCP). This study examined relationships between longitudinal patterns of illicit/prescription drug use/misuse and cannabis practices among young adult cannabis users.<bold>Design and Methods: </bold>In 2014-2015, 210 young adult MCP and 156 nonpatient users were recruited in Los Angeles and surveyed annually over four waves. The analytical sample was limited to completers of all four waves (n = 301). Distinct developmental trajectories of illicit drug use and prescription drug misuse were identified. Fixed effects regression analysis evaluated changes in cannabis practices by trajectory groups.<bold>Results: </bold>Results supported two-trajectory solutions (high/low) for illicit drug use and prescription drug misuse. Decreases in use within all four trajectories occurred by wave 4. Low illicit drug use trajectory members were more likely to self-report medical cannabis use. Membership in both types of high-use trajectories was associated with use of concentrates and edibles. The prevalence of MCP, edibles use and cannabis days decreased significantly by wave 4.<bold>Discussion and Conclusions: </bold>While alternative cannabis forms use was associated with membership in high drug use trajectories, self-reported medical cannabis use (not MCP) was negatively associated with high illicit drug use trajectory membership. Reductions in the prevalence of MCP, cannabis days, edibles use and other drug use by wave 4 alongside stable levels of self-reported medical cannabis use might reflect the changing legal status of cannabis in California, maturing out phenomenon and safer patterns of cannabis use. [ABSTRACT FROM AUTHOR]