Marijuana May Raise, Not Reduce, Risk for Opioid Use Disorder

Megan Brooks

February 02, 2018

Contrary to current thinking, a new study suggests that individuals who use marijuana may be at increased risk of developing an opioid use disorder.

"The notion that marijuana can help curb the opioid epidemic has received a fair amount of media attention. This study calls into question the assumption that broader public use of recreational marijuana will somehow lead to a reduction in nonmedical use of prescription opioids," lead author Mark Olfson, MD, MPH, of Columbia University, New York City, told Medscape Medical News.

"While the results of this study don't address potential benefits of medical marijuana for people with painful medical conditions, the findings do highlight a potential risk," he added.

The study was published in the January issue of the American Journal of Psychiatry.

Significant Increased Risk

Dr Olfson and colleagues examined ties between marijuana use at wave 1 (2001-2002) and nonmedical prescription opioid use and prescription opioid use disorder at wave 2 (2004-2005) in the National Epidemiologic Survey on Alcohol and Related Conditions, which has more than 35,000 adult participants.

Nonmedical use of a prescription opioid was defined as use of a prescription analgesic "without a prescription, in greater amounts, more often, or longer than prescribed, or for a reason other than a doctor said you should use them" during the 12 months preceding the interview.

After controlling for patient characteristics (age, sex, race/ethnicity, family history, other substance use disorders, and wave 1 mood and anxiety disorders and nonmedical opioid use), cannabis use at wave 1 was associated with prevalent nonmedical opioid use (adjusted odds ratio [aOR], 3.54; 95% confidence interval [CI], 2.74 - 4.57) and initiation of nonmedical use of opioids (aOR, 2.62; 95% CI, 1.86 - 3.69) at wave 2.

Among adults with nonmedical opioid use at wave 1, cannabis use was also associated with an increase in nonmedical opioid use at wave 2 (adjusted OR, 3.13; 95% CI, 1.19 - 8.23).

In those with moderate to severe pain at wave 1, cannabis use was also associated with increased incident nonmedical opioid use (aOR, 2.99; 95% CI, 1.63 - 5.47) at wave 2, and with increased incident prescription opioid use disorder, although the association fell short of significance (aOR, 2.14; 95% CI, 0.95 - 4.83).

Development of an opioid use disorder at wave 2 occurred more often in people who were occasional (2.9%), frequent (4.3%), or very frequent (4.4%) marijuana users at wave 1 than in nonusers (0.5%).

"Contrary to some previous reports that were based on population-level patterns, marijuana use tended to increase rather than decrease the risk of prescription opioid use disorder," said Dr Olfson.

"Even though a great majority of those who smoked marijuana at the start of the study did not develop an opioid problem, they were at significantly elevated risk of developing these problems," he added.

"Critical Contribution"

In an accompanying editorial, Dennis McCarty, PhD, from Oregon Health and Science University–Portland State University, notes that although this study does not resolve the debate about associations between medical cannabis use, use of prescription opioids, and risks for opioid overdose mortality, it is "an important contribution that balances the state-level analyses with individual-level data. The contrasting associations from the state-level and the person-level analyses should serve as a caution to eager advocates and puzzled policy makers."

Dr McCarty says it's important to realize that today's marijuana products are not the simple "weed" of the 1960s and 1970s. Selective breeding has produced cannabis strains with much higher tetrahydrocannabinol (THC) levels, and entrepreneurs are marketing cannabis concentrates that are ingested and inhaled using a variety of devices.

"The potential harms and benefits of the THC concentrates are unknown," he notes.

He believes it's time for states that have legalized cannabis to build patient registries of cannabis that are linked to medical records so that it is possible to assess morbidity and mortality data associated with the frequency, duration, and method of using various forms of cannabis (eg, buds, hash, oils, resins, dabs, and candies via pipes, bongs, vaporizers, lozenges, and lotions).

This study, Dr McCarty concludes, "is a critical contribution and will stimulate development of new analyses and more complete understandings of the complex relations between cannabis, medical cannabis, and opioid prescribing and use."

The study was supported by the National Institutes of Health. Dr Olfson and Dr McCarty have disclosed no relevant financial relationships.

Am J Psychiatry. 2018;175:6-7, 47-53. Abstract, Editorial

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