Further, changing attitudes may also underlie the movement toward marijuana legalization, now enacted in 23 states for medical purposes and in 4 states for recreational purposes.1–3 Passage of these and additional laws may further change attitudes and beliefs in a permissive direction, as suggested in one study,57 an issue requiring further research. Further, while the details of state marijuana laws vary58,59 and arguments are made both for and against these legal changes,60–62 all forms of legalization increase the availability of marijuana in some manner. Medical marijuana laws have little effect on adolescent recreational marijuana use3,63–66 but may affect adult risk.66 A concern about greater legalization for recreational use is that financial interests in marijuana sales and tax revenue could promote increased use. Our study clearly cannot predict the impact of further legalization. However, using alcohol and nicotine as models, changes in laws and policies (eg, minimum legal drinking age and smoke-free laws) do appear related to changes in use and consequences, suggesting that the legal status of marijuana could influence the risk for marijuana use disorders, particularly if legalization of
