Rising problematic use in US states where marijuana is legal

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Problematic use of marijuana among adolescents and adults increased after legalisation of recreational marijuana use, according to a study from the New York University Grossman School of Medicine and Columbia University Mailman School of Public Health, reports ScienceDaily.

Published online 13 November in JAMA Psychiatry, the study is the first to look at the impact of recreational marijuana legalisation on both use and cannabis use disorder (commonly referred to as problematic marijuana use) across multiple age groups.

Presently, 11 states and Washington DC have legalised marijuana for recreational use while 33 states and DC have legalised marijuana for medical use, reports the study material from New York University.

After examining usage following the enactment of marijuana legalization in 2012 to 2015, the researchers found that:

  • Problematic use among adolescents aged 12 to 17 was 25% higher (a small increase from 2.18% to 2.72%) compared to states without legal recreational use. There was no change in the prevalence of past-month or frequent use among teens.
  • Among adults aged 26 or older, past-month marijuana use after legalisation was 26% higher than in non-recreational states. Past-month frequent use rose by 23%, and past-year problematic use increased by 37%.
  • Among young adults aged 18 to 25, there was no difference found in past-month, frequent or problematic marijuana use.

“There are, indeed, important social benefits that legalising marijuana can provide, particularly around issues of equity in criminal justice,” said Magdalena Cerdá, Associate Professor and Director of the Center for Opioid Epidemiology and Policy in the Department of Population Health at NYU Langone Health, and the study’s lead author.

“Our findings suggest that as more states move toward legalising marijuana for recreational use, we also need to think about investing in substance use prevention and treatment to prevent unintended harms – particularly among adolescents.”

How the study was conducted

Cerdá and colleagues analysed data from the National Survey on Drug Use and Health (NSDUH) with a sample of 505,796 respondents. The investigators specifically looked at data from Colorado, Washington, Alaska and Oregon from 2008-2016, the first four states to legalise marijuana for recreational use, so they could track trends in marijuana use before and after legalisation.

They compared trends in these four states to trends in states that had not legalized recreational marijuana use. The team examined marijuana use and frequent use (more than 20 days) in the past month, and cannabis use disorder over the past year.

Respondents were classified as having cannabis use disorder based on symptoms corresponding to DSM-IV criteria, which include increased tolerance, repeated attempts to control use or quit, spending a lot of time using, social interpersonal problems due to use, and giving up other activities to use, to name a few.

“Cannabis use disorder in adolescence is associated with long-term adverse health, economic and social consequences,” said Silvia S Martins, Associate Professor of Epidemiology at Columbia University Mailman School of Public Health, Director, Center on Policy and Health Initiatives on Opioids and Other Substances (PHIOS), and the study’s senior author. “Given our findings on problematic use across age groups, legalisation efforts should coincide with prevention and treatment. The general public should be informed about both benefits and potential harms of marijuana products to make informed decisions.”

To determine if increase among adolescents could be attributable to other factors besides legalisation – such as the introduction of higher-potency cannabis products by the illegal market in the same states that legalised recreational marijuana use – the researchers conducted a sensitivity analysis.

They found that if other, unmeasured factors that slightly increased the risk of cannabis use disorder became more prevalent in states that legalised recreational marijuana use at the same time as legalisation, those unknown factors could explain the relationship. The extent to which those confounders exist, according to Cerdá, remains unclear and more studies are necessary.

Study limitations

The researchers identify the study’s limitations. First, findings were reliant on self-reported marijuana use; it is possible that more people may report use following legalisation because of increased social acceptability. Secondly, frequency of use and cannabis use disorder are only two aspects of marijuana use.

Future studies, according to Cerdá and colleagues, should investigate additional measures such as frequency of use within days and THC potency in marijuana products for a more comprehensive assessment of how recreational legalisation affects use.

Association Between Recreational Marijuana Legalization in the United States and Changes in Marijuana Use and Cannabis Use Disorder From 2008 to 2016

JAMA Psychiatry, 13 November 2019


Magdalena Cerdá, Christine Mauro, Ava Hamilton et al, Natalie S. Levy, Julian Santaella-Tenorio, Deborah Hasin, Melanie M Wall, Katherine M Keyes and Silvia S Martins.

Key Points

Question: How did marijuana use and cannabis use disorder change during 2008 to 2016 after the legalisation of recreational marijuana in the United States?

Findings: In this multilevel, difference-in-difference survey study with 505 796 respondents comparing marijuana use before and after the legalisation of recreational marijuana in the United States, the proportion of respondents aged 12 to 17 years reporting cannabis use disorder increased from 2.18% to 2.72%, while the proportion of respondents 26 years or older reporting frequent marijuana use increased from 2.13% to 2.62% and those with cannabis use disorder, from 0.90% to 1.23%.

Meaning: This study’s findings suggest that possible increases in the risk for cannabis use disorder among adolescent users and increases in frequent use and cannabis use disorder among adults after legalization of recreational marijuana use may raise public health concerns and warrant ongoing study.


Importance: Little is known about changes in marijuana use and cannabis use disorder (CUD) after recreational marijuana legalization (RML).

Objectives: To examine the associations between RML enactment and changes in marijuana use, frequent use, and CUD in the United States from 2008 to 2016.

Design, setting and participants: This survey study used repeated cross-sectional survey data from the National Survey on Drug Use and Health (2008-2016) conducted in the United States among participants in the age groups of 12 to 17, 18 to 25, and 26 years or older.

Interventions: Multilevel logistic regression models were fit to obtain estimates of before-vs-after changes in marijuana use among respondents in states enacting RML compared to changes in other states.

Main outcomes and measures: Self-reported past-month marijuana use, past-month frequent marijuana use, past-month frequent use among past-month users, past-year CUD, and past-year CUD among past-year users.

Results: The study included 505 796 respondents consisting of 51.51% females and 77.24% participants 26 years or older. Among the total, 65.43% were white, 11.90% black, 15.36% Hispanic, and 7.31% of other race/ethnicity. Among respondents aged 12 to 17 years, past-year CUD increased from 2.18% to 2.72% after RML enactment, a 25% higher increase than that for the same age group in states that did not enact RML (odds ratio [OR], 1.25; 95% CI, 1.01-1.55). 

Among past-year marijuana users in this age group, CUD increased from 22.80% to 27.20% (OR, 1.27; 95% CI, 1.01-1.59). Unmeasured confounders would need to be more prevalent in RML states and increase the risk of cannabis use by 1.08 to 1.11 times to explain observed results, indicating results that are sensitive to omitted variables. No associations were found among the respondents aged 18 to 25 years.

Among respondents 26 years or older, past-month marijuana use after RML enactment increased from 5.65% to 7.10% (OR, 1.28; 95% CI, 1.16-1.40), past-month frequent use from 2.13% to 2.62% (OR, 1.24; 95% CI, 1.08-1.41), and past-year CUD from 0.90% to 1.23% (OR, 1.36; 95% CI, 1.08-1.71); these results were more robust to unmeasured confounding. Among marijuana users in this age group, past-month frequent marijuana use and past-year CUD did not increase after RML enactment.

Conclusions and relevance: This study’s findings suggest that although marijuana legalisation advanced social justice goals, the small post-RML increase in risk for CUD among respondents aged 12 to 17 years and increased frequent use and CUD among adults 26 years or older in this study are a potential public health concern.

To undertake prevention efforts, further studies are warranted to assess how these increases occur and to identify subpopulations that may be especially vulnerable.

In states where recreational marijuana is legal, problematic use increased among adults and teens

Association Between Recreational Marijuana Legalization in the United States and Changes in Marijuana Use and Cannabis Use Disorder From 2008 to 2016

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