Medical Marijuana Laws and Cannabis Use

Abstract
Cannabis is the most commonly used illicit drug in the United States,1 and with the proliferation of states legalizing marijuana for medical and/or recreational purposes, attention has been focused on a potential rise in use and related problems. Primary attention has been on rates of use among youth, as early adolescent use has been linked to an increased risk for addiction to cannabis and other drugs. To our knowledge, research to date has not documented an increase in cannabis use by adolescents in the United States overall1 or in those states that enacted new marijuana laws.2,3 However, the issue of whether changes in marijuana laws and policies affect use of cannabis by adults is also a concern and is the topic addressed by Hasin et al4 in this issue of JAMA Psychiatry. In their study, they analyzed epidemiological data from the past 25 years and confirmed earlier reports2,3 that changes in medical marijuana laws appear to be associated with increases in cannabis use and disorders among adults.