Marijuana use did not affect HIV prevention pill adherence among gay and bisexual men | Research

The takeaway

Among 104 PrEP-using gay and bisexual men tracked over 10 weeks, marijuana use and heavy drinking did not affect daily PrEP adherence, while club drug use increased the odds of missing a dose by 55-60%.

Cannabis users on daily medications, people interested in HIV prevention, and clinicians counseling patients about substance use and medication adherence.

Marijuana and heavy drinking: zero effect on PrEP adherence across 9,532 person-days

What the researchers found

No event-level effect of marijuana use or heavy drinking on PrEP adherence was found. Club drug use increased odds of missing PrEP by 55% same-day and 60% next-day. Missing one dose increased odds of missing the next day by eightfold. Club drug users averaged 1.6 missed doses in 30 days.

Why it matters

Concerns that cannabis might interfere with medication adherence are not supported here. For HIV prevention specifically, cannabis use does not appear to compromise the effectiveness of daily PrEP, while club drugs do present a genuine risk.

The numbers in context

104 participants, 9,532 days of data, 10 weeks. Club drugs: 55% increased odds same-day, 60% next-day (carryover effect). Missing one dose: 8x odds of missing the next day. Marijuana: no significant effect. Heavy drinking: no significant effect.

How the study worked

Retrospective 30-day timeline follow-back interviews plus prospective semi-weekly diaries for 10 weeks with 104 PrEP-using gay and bisexual men (half club drug users), generating 9,532 person-days of data.

What this study cannot tell us

Small sample (n=104). Self-reported substance use and PrEP adherence. All participants were from one city. Club drug use was the primary research focus, with marijuana as a secondary analysis.

How to read the evidence

Moderate: prospective daily diary data with detailed substance tracking, though small sample.

When this study was published

Published in 2019.

The bigger picture

This distinction between substance types matters for clinical counseling. Rather than warning PrEP users about all substance use broadly, clinicians can focus their attention on the specific substances that actually compromise adherence.

Questions still open

Would these findings hold in larger, more diverse samples? Does cannabis use affect adherence to other medications or just PrEP? Could the lack of marijuana effect reflect lower intoxication severity compared to club drugs?

Common questions

Does marijuana make you forget to take medications?

Not according to this study. Marijuana use showed no significant effect on daily PrEP adherence across nearly 10,000 person-days of data. Club drugs (cocaine, ecstasy, ketamine) did increase missed doses by 55-60%.

Why did missing one dose matter so much?

Missing one PrEP dose increased odds of missing the next day by 8x, creating a cascading effect. This pattern was driven by club drug use events, not marijuana, suggesting club drugs create multi-day disruptions to routine.

Read the original research

Determining the Roles that Club Drugs, Marijuana, and Heavy Drinking Play in PrEP Medication Adherence Among Gay and Bisexual Men: Implications for Treatment and Research.

AIDS and behavior, 23(5), 1277-1286

View on PubMed ↗Publisher’s paper ↗

Citation

Grov, Christian; Rendina, H Jonathon; John, Steven A; Parsons, Jeffrey T. (2019). Determining the Roles that Club Drugs, Marijuana, and Heavy Drinking Play in PrEP Medication Adherence Among Gay and Bisexual Men: Implications for Treatment and Research.. AIDS and behavior, 23(5), 1277-1286. https://doi.org/10.1007/s10461-018-2309-9