April 26, 2017
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Medical marijuana laws influence increases in cannabis use, disorder

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States that passed medical marijuana laws experienced greater increases in illicit cannabis use and cannabis use disorder than states that did not pass such laws, suggesting an association between the two.

“As of November 2016, 28 states have passed medical marijuana laws. Many adults now favor legalizing recreational use, and fewer view cannabis as risky. Despite this view, while some can use cannabis without harm, potential consequences include impaired functioning, vehicle crashes, ED visits, psychiatric symptoms, and addiction,” Deborah S. Hasin, PhD, of Columbia University Medical Center, and colleagues wrote. “Over time, the prevalence of adult illicit use and related consequences has increased. Thus, identifying factors underlying increased adult illicit use is important. State [medical marijuana laws] may be one such factor.”

Deborah Hasin
Deborah S. Hasin

To determine differences in prevalence of cannabis use and disorders between individuals living in states with or without medical marijuana laws, researchers analyzed data from the 1991 to 1992 National Longitudinal Alcohol Epidemiologic Survey (NLAES), the 2001 to 2002 National Epidemiologic Survey on Alcohol and Related Conditions (NESARC), and the 2012 to 2013 National Epidemiologic Survey on Alcohol and Related Conditions–III (NESARC-III).

From 1991-1992 to 2012-2013, illicit cannabis use (P = .004) and cannabis use disorders (P = .03) increased more in states that passed medical marijuana laws than those that did not.

From 1991-1992 to 2001-2002, illicit cannabis use and disorders decreased among states without medical marijuana laws and in California.

Conversely, illicit cannabis use (P = .004) and disorders (P = .02) differed between states that passed laws early in the study period and those that did not pass medical marijuana laws.

From 2001-2002 to 2012-2013, illicit cannabis use increased by 3.5 percentage points in states that never passed medical marijuana laws; 5.3 points in California; 7 points in Colorado; 2.6 points in states that passed laws earlier; and 5.1 points in states that passed laws later.

Compared with states that never passed medical marijuana laws, increases in use were greater in states that passed laws later (P = .01), California (P = .04) and Colorado (P = .03).

Increases in cannabis use disorder were smaller but similar to changes in use, with greater changes in California (P = .06) and Colorado (P = .04), compared with states that never passed medical marijuana laws.

“Understanding the nuances of the laws to determine which components of a policy are associated with positive and negative effects and to balance potential harms and benefits should be necessary considerations for policymakers and those implementing state laws,” Wilson M. Compton, MD, MPE, of the National Institute on Drug Abuse, and colleagues wrote in an accompanying editorial. “While research continues to gather evidence to that end, clinicians are faced with the reality reinforced by the findings from Hasin et al that cannabis use is increasing among adults living in states that have legalized medical marijuana. In the meantime, it is clear that a robust system of education, prevention, and treatment is needed to minimize the negative consequences that might arise if cannabis use continues to increase.” – by Amanda Oldt

Disclosure: Hasin reports no relevant financial disclosures. Please see the study for a full list of relevant financial disclosures.