In the summer of 1996 proposition 216, California’s Compassionate Use Act, essentially legalized marijuana use with a prescription by a physician (“medical marijuana”) and in 2012, Colorado passed Amendment 64 (which legalized marijuana use in Colorado without any requirement for a prescription) – all of a sudden we were conducting a population based study of the impact of marijuana use and mental health symptoms and psychosis.
Early Studies on Changes in Marijuana Use and Impact on Mental Health
Studies indicated a large increase in marijuana use. 12.5% of persons age 18 or older in the United States reported past-year use of cannabis in 2013, this was about 19% higher than the 10.5% found in 2002. As cannabis use became normalized in society people were more likely to use it. This seemed to be particularly true among young adults.
An analysis of the data from the National Epidemiologic Survey on Alcohol and Related Conditions – III (NESARC-III – a nationally representative survey of 46,500 adult Americans that collected data on alcohol use disorders and their associated disabilities) by Hasin and colleagues, found evidence of a significant association between cannabis use and a number of psychiatric conditions.
In editorial accompanying the article, Wilson M. Compton, M.D., M.P.E. and Ruben Baler, Ph.D. wrote that –
Cannabis use disorder was found to be prevalent, with a past-year rate of 2.5% and a lifetime rate of 6.3%. Rates were higher among men, Native Americans, unmarried persons, younger persons, and those with low incomes. Comorbidity was found to be common, with strong associations of cannabis use disorder with other substance use disorders, affective disorders, anxiety disorders, and personality disorders… Hasin and colleagues found that increasing DSM-5 cannabis use disorder severity was also associated with poorer functioning and stronger correlation with risk factors.
2022 Data Strengthens Evidence of a Strong Effect of Heavier Marijuana Use and Psychotic Symptoms
In 2022, a follow up study by Livne and colleagues looked at newer data from the NESARC project. found even more compelling evidence for a link between marijuana use and psychotic symptoms. Among daily users and users who met criteria for cannabis use disorder, that is to say among the heaviest users, ten times as many people reported psychotic symptoms as among non-users of marijuana. This is a very large difference in risk, one of the strongest associations between a substance use disorder and a mental health disorder that has ever been reported.
Pacula R, Jacobson M, Maksabedian EJ: In the weeds: a baseline view of cannabis use among legalizing states and their neighbours. Addiction (Epub ahead of print, Dec 21, 2015)
Grucza RA, Agrawal A, Krauss MJ, et al: Recent trends in the prevalence of marijuana use and associated disorders in the United States. JAMA Psychiatry 2016; 73:300–301
Blanco C, Hasin DS, Wall MM, et al: Cannabis use and risk of psychiatric disorders: prospective evidence from a US national longitudinal study. JAMA Psychiatry (Epub ahead of print, Feb 17, 2016)
Volkow ND, Baler RD, Compton WM, et al: Adverse health effects of marijuana use. N Engl J Med 2014; 370:2219–2227
Hasin DS, Kerridge BT, Saha TD, et al: Prevalence and correlates of DSM-5 cannabis use disorder, 2012–2013: findings from the National Epidemiologic Survey on Alcohol and Related Conditions–III. Am J Psychiatry 2016; 173:588–599
Compton WM, Thomas YF, Conway KP, et al: Developments in the epidemiology of drug use and drug use disorders. Am J Psychiatry 2005; 162:1494–1502
Hasin DS, O’Brien CP, Auriacombe M, et al: DSM-5 criteria for substance use disorders: recommendations and rationale. Am J Psychiatry 2013; 170:834–851
Batalla A, Bhattacharyya S, Yücel M, et al: Structural and functional imaging studies in chronic cannabis users: a systematic review of adolescent and adult findings. PLoS One 2013; 8:e55821
Filbey F, Yezhuvath U: Functional connectivity in inhibitory control networks and severity of cannabis use disorder. Am J Drug Alcohol Abuse 2013; 39:382–391
Zalesky A, Solowij N, Yücel M, et al: Effect of long-term cannabis use on axonal fibre connectivity. Brain 2012; 135:2245–2255
Ofir Livne, Dvora Shmulewitz, Aaron L. Sarvet, Melanie M. Wall, and Deborah S. Hasin. Association of Cannabis Use–Related Predictor Variables and Self-Reported Psychotic Disorders: U.S. Adults, 2001–2002 and 2012–2013. American Journal of Psychiatry 2022 179:1, 36-45