Illicit Cannabis Use Among Adults Up Due to Medical Marijuana Laws

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The associations between rates of cannabis use, cannabis use disorder, and changes in medical marijuana laws require further study.
The associations between rates of cannabis use, cannabis use disorder, and changes in medical marijuana laws require further study.

Medical marijuana laws (MML) may be connected to increased rates of illicit cannabis use and cannabis use disorder, according to new research published in JAMA Psychiatry.1

By the end of 2016, medical marijuana laws (MML) had been passed in 28 US states, and public support for the legalization of recreational marijuana use has risen substantially.2 Although cannabis is now viewed as less risky than previously, some users do experience negative consequences, including motor vehicle accidents, emergency room visits, and addiction.3-5

The prevalence of such consequences has increased in conjunction with the prevalence of illicit marijuana use among adults, highlighting the need to elucidate factors driving increased use, according to the study.

Deborah S. Hasin, PhD, of the department of psychiatry, Columbia University Medical Center, New York, New York, and colleagues, proposed that MML could be one underlying factor, although few studies have investigated this association. In the present research, they analyzed data from 3 cross-sectional epidemiologic surveys of US adults that took place 1991-1992, 2001-2002, and 2012-2013 to examine changes in illicit cannabis use, cannabis use disorders, and MML between these various points and over the entire timespan.

At the time of the first study, no states had MML laws; at the time of the second study, 18.9% of Americans lived in MML states; and during the third study, more than one-third of Americans lived in MML states. Each survey inquired about illicit cannabis use within the previous 12 months, and DSM-IV substance abuse was assessed with the Alcohol Use Disorder and Associated Disabilities Interview Schedule (AUDADIS).

The findings revealed the following:

  • From 1991-1992 to 2012-2013, there was a greater increase in illicit cannabis use (up 1.4%; SE, 0.5; P =.004) and cannabis use disorders (0.7% increase; SE, 0.3; P =.03) in MML states compared with other states.
  • In the period between 1991-1992 and 2001-2002, illicit use and disorders showed a similar decline in non-MML states and California (which had a higher prevalence at the beginning of the first study).
  • In other early-MML states, however, there was an increase in the prevalence of use and use disorders during the same period, and there were differences between these states and non-MML states in both use (+2.5%; SE, 0.9; P =.004) and disorders (+1.1%; SE, 0.5; P =.02).
  • In the period between 2001-2002 and 2012-2013, illicit use increased as follows: 3.5% in never-MML states (SE, 0.5), 5.3% in California (SE, 1.0), 7.0% in Colorado (SE, 1.6), 2.6% in other early-MML states (SE, 0.9), and 5.1% in late-MML states (SE, 0.8).
  • During this period, there were greater increases in illicit use in late-MML states vs never-MML states (+1.6%; SE, 0.6; P =.01), California (+1.8%; SE, 0.9; P =.04), and Colorado (+3.5%; SE, 1.5; P =.03).
  • While cannabis use disorder was less prevalent and showed smaller increases during this period, it followed similar patterns, with greater change in California (+1.0%; SE, 0.5; P =.06) and Colorado (+1.6%; SE, 0.8; P =.04) compared with never-MML states.

Additional studies are needed to further explore the associations between rates of cannabis use, cannabis use disorder, and changes in MML, as well as potential mechanisms underlying these links, the investigators concluded.

References

  1. Hasin DS, Sarvet AL, Cerdá M, et al. US adult illicit cannabis use, cannabis use disorder, and medical marijuana laws: 1991-1992 to 2012-2013. JAMA Psychiatry. 2017;74(6):579-588. doi:10.1001/jamapsychiatry.2017.0724
  2. Gallup. Majority continues to support pot legalization in US. www.gallup.com/poll /179195/majority-continues-support-pot-legalization.aspx. Accessed July 28, 2017.
  3. Brady JE, Li G. Trends in alcohol and other drugs detected in fatally injured drivers in the United States, 1999-2010.   Am J Epidemiol. 2014;179(6):692-699. doi:10.1093/aje/kwt327
  4. Zhu H, Wu LT. Trends and correlates of cannabis-involved emergency department visits: 2004 to 2011. J Addict Med. 2016;10(6):429-436. doi:10.1097/ADM.0000000000000256
  5. Bonn-Miller MO, Harris AH, Trafton JA. Prevalence of cannabis use disorder diagnoses among veterans in 2002, 2008, and 2009. Psychol Serv. 2012; 9(4):404-416. doi:10.1037/a0027622
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