Cannabis Use Disorders
Over the last 25 years, cannabis use and cannabis use disorders have increased among US adults and 28 states have passed medical marijuana laws (MML). Still, little is known about the impact of MML and the illicit use of cannabis use and cannabis use disorders by adults during this time frame. In a recent study (June 2017), Hasin and colleagues summarized the trend in cannabis use from 1991-1992 and from 2012-2013. The results showed illicit cannabis use increased significantly more in states that passed MML than in other states (1.4–percentage point more; SE, 0.5; P = .004), as did cannabis use disorders (0.7–percentage point more; SE, 0.3; P = .03).
For psychiatrists, primary care physicians and addiction medicine doctors, understanding the effect of new marijuana laws is important because of the potential effect of cannabis on mental and physical health. To start with, individuals with mental illness are more likely to use marijuana for self-medication. Both acute intoxication and chronic use exacerbate psychiatric symptoms. Also, early cannabis use is associated with onset of psychosis and increased risk for suicidality among teens and young adults. Moreover, cannabis use interferes with the treatment of mental health disorders. Understanding the potential effect of cannabis use on mental illness is advanced by careful population studies, as cited above. In recent years, the potency of cannabis (Δ9-tetrahydrocannabinol content) has increased three-fold to four-fold, and the ways in which users consume cannabis have also changed, raising questions as to how these factors may or may not increase the potential for harm.
Why Does This Matter?
Concurrently, the legal landscape regarding cannabis, including both medical and recreational legalization, has evolved rapidly. This begs the question as to whether the legal changes are influencing the rates of cannabis use and cannabis use disorder. In addition, these data are raising concern regarding underage use since there is strong and consistent science warning about adolescents smoking marijuana and brain changes/development. Lastly, the concerns regarding the increasing potency of cannabis and the ensuing harmful effects– including addiction, accidents, learning and mental disorders, under achievement and concurrent smoking of MJ and tobacco with premature death.