The 2001–2002 to 2012–2013 period saw a substantial increase in the prevalence of marijuana use, and because marijuana use disorder prevalence did not increase among users, the findings indicate that the increased prevalence of marijuana use disorder over the last decade can be attributed to the increased prevalence of marijuana users in the general population. With a greater proportion of adults at risk for marijuana use disorders because they were users, a greater proportion of them developed disorders. This parallels national increases in marijuana use disorders54 and other marijuana-related problems17,19 found in other studies over the same general period. Identifying factors leading to these increases is crucial to reversing the trends and preventing future increases. One possible factor is changes in the belief that marijuana use is risky, the prevalence of which has decreased sharply among adults and adolescents in recent years.5,6 Given the robust connection between beliefs about riskiness and actual use,55 changes in such beliefs may play an important role. Therefore, public education about the risks of marijuana use, presented in a reasonable, balanced manner,56 appears increasingly important to counteract public beliefs that marijuana use is harmless.
