“Marijuana use has become increasingly popular in the United States since the turn of the century, and typical use patterns among past-month 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.
Dependence among DND users fell by 39% (26.5%-16.1%; p < .001), with significant trend. 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: reducing important activities (p < .001); use despite emotional, mental, or physical problems (p < .001); failing attempts to cutback (p < .001); lots of time getting, using, or getting over marijuana (p < .01); and failing to keep limits set on use (p < .05). Reported tolerance showed no significant change.
Though it is unclear why, the risk of dependence formation among heavy marijuana users appear to have declined since 2002. Further research is warranted regarding explanations related to state marijuana policies, product forms, or social context.”