Falling Rates of Marijuana Dependence Among Heavy Users

Introduction Marijuana use has become increasingly popular in the United States since the turn of the century, and typical use patterns among current marijuana users have intensified, raising concerns for an increase in cannabis use disorders (CUDs). Yet the population prevalence of CUDs has mostly remained flat. We analyzed trends in DSM-IV marijuana dependence among Daily/Near-Daily (DND) users, both overall and by age and gender, and considered potential explanations. Methods Using data assembled from the National Survey on Drug Use and Health (2002-2016), rates of self-reported dependence and constituent symptoms are calculated for DND marijuana users; logistic regressions with pre- and post- periods (2002-2004, 2014-2016) are applied to describe temporal changes. Results Dependence among DND users fell by 39% (26.5%-16.1%; p<0.001). No significant change is detected at the population level. Sub-group analysis shows a steep gradient for age but not for gender. Declines are robust to sub-group analysis, except for users over 50 years old. Among dependence symptoms, most showed significant declines: giving up important activities (p<0.001); continued use despite emotional, mental, or physical problems (p<0.001); failing attempts to reduce use (p<0.001); spending lots of time getting, using, or getting over marijuana (p<0.01); and failing to keep limits set on use (p<.05). Reported tolerance showed no significant change. Conclusions Though it is unclear why, the risk of dependence formation among heavy marijuana users appear to have declined substantially since 2002. Further research is warranted to search for explanations related to state marijuana policies, product forms, or social context.