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

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.