Although many users of cannabis do not view smoking marijuana as harmful, a new study has found that cannabis use is linked to substance use disorders. The findings were published online on February 17 in the journal JAMA Psychiatry.
The authors note that the soaring rates of recreational marijuana use and the changing legal status of cannabis across the US have fueled debate regarding the mental health consequences of cannabis use. Medical use of cannabis may benefit a selected group of patients; however, scientific evidence supporting these claims remains limited, while the adverse effects of cannabis use have been extensively documented. Research focused on the increased health consequences associated with overuse of prescription opioids underscores potential health threats posed by broad access to drugs with addictive liability. Relationships between increased availability of psychoactive substances and population-level adverse health outcomes raise critical public health policy questions regarding potential harms associated with expanded access to those substances.
In view of the foregoing, the researchers examined associations between cannabis use and risk of mental health and substance use disorders in the general adult population. The study group comprised a nationally representative sample of US adults aged 18 years or older; they were interviewed three years apart in the National Epidemiologic Survey on Alcohol and Related Conditions (wave 1: 2001-2002; wave 2: 2004-2005). The primary evaluations were limited to 34,653 respondents who were interviewed in both waves. Data analysis was conducted from March 15 through November 30, 2015.
Psychiatric disorders were measured with a structured interview (Alcohol Use Disorder and Associated Disabilities Interview Schedule–DSM-IV). In both analyses, the same set of wave 1 confounders (factors that could skew the data) was used, including sociodemographic characteristics, family history of substance use disorder, disturbed family environment, childhood parental loss, low self-esteem, social deviance, education, recent trauma, past and present psychiatric disorders, and respondent’s history of divorce.
The investigators found that analysis of 34,653 respondents (14,564 male [47.9%]; average age 45.1 years), cannabis use in wave 1 (2001-2002), which was reported by 1,279 respondents, was significantly associated with substance use disorders in wave 2 (2004-2005) (any substance use disorder: 6.2-fold increased risk; any alcohol use disorder: 2.7-fold increased risk; any cannabis use disorder: 9.5-fold increased risk; any other drug use disorder: 2.6-fold increased risk; and nicotine dependence: 1.7-fold increased risk), but not any mood disorder (1.1-fold increased risk) or anxiety disorder (0.1-fold decreased risk). The same general pattern of results was observed in the analyses of wave 2 prevalent psychiatric disorders and in the propensity score–matched analysis of incident and prevalent psychiatric disorders.
The authors concluded that, within the general population, cannabis use is associated with an increased risk for several substance use disorders. They recommended that physicians and policy makers should take these associations of cannabis use under careful consideration.
The authors are affiliated with: Division of Epidemiology, Services, and Prevention Research, National Institute on Drug Abuse, Bethesda, Maryland; Department of Psychiatry, Columbia University Medical Center/New York State Psychiatric Institute, New York; Assistance Publique-Hôpitaux de Paris, Corentin Celton Hospital, Paris, France; Department of Psychiatry, Paris Descartes University, Pôle de Recherche et d’Enseignement Supérieur Sorbonne Paris Cité, Paris, France; and Institut National de la Santé et de la Recherche Médicale Unité Mixte de Recherche 894, Psychiatry and Neurosciences Center, Paris Descartes University, PRES Sorbonne Paris Cité, Paris, France.