The Impact of Marijuana Use on Medically Assisted Opioid Treatment

The Canadian Parliament recently approved the legalization of cannabis beginning in 2018. Like the experience in many states in the U.S., this was a political decision and not based upon empirically derived evidence regarding the potential safety or benefits of cannabis. Of particular interest alongside the current opioid crisis is the use of cannabis among persons with opioid use disorder.

Marijuana and Medically Assisted Opioid Treatment

Behind alcohol, marijuana use disorder is the second leading reason patients enter addiction treatment. Like alcohol, lifetime use of marijuana is nearly ubiquitous and an established “gateway” drug. Thus, most patients in treatment for opioid use disorder began their illicit drug use with marijuana, and most continue to use it. Patients engaged in medication-assisted treatment (MAT) for opioid use disorder seldom recognize the harmful effects of cannabis use, and the combined effects are largely unknown.

In this retrospective cohort study, blinded electronic medical records from 58 clinics utilizing MAT were employed to determine how outcomes are impacted by gender. A 12-month treatment retention was the primary end point and the outcome of interest. Data was attained and analyzed for patients based upon the results of their cannabis urine sample in their first month of treatment and subsequent urine samples throughout each patient’s MAT.

Of the 644 study participants, 328 of were classified as baseline cannabis users and 256 as heavy users. The results revealed that both groups were at increased risk of treatment dropout (38.9% and 48.1%, respectively). Analysis of these data by gender revealed that female baseline cannabis users and male heavy cannabis users are at increased risk of premature dropout of MAT.

The research concluded that although both baseline and heavy cannabis use is predictive of decreased treatment retention, differences observed between genders is significant, but the reason for this is not clear.

Why Does This Matter?

As marijuana legalization is becoming common while we still do not fully understand the implications, physicians should more closely monitor cannabis-using patients and offer more education regarding the potential harms associated with marijuana use, particularly for those receiving treatment for opioid use disorder.