Marijuana Use Cut the Odds of Successfully Quitting Tobacco in Half | Research

The takeaway

Among 1,481 smokers attempting to quit with nicotine patches, marijuana users were only half as likely to succeed, making cannabis use one of the strongest negative predictors of tobacco cessation.

Read this if you use both cannabis and tobacco and are trying to quit smoking.

Marijuana users had half the odds of successfully quitting tobacco

What the researchers found

Researchers followed 1,481 heavy smokers (averaging 32 cigarettes per day) through a 26-week smoking cessation program using transdermal nicotine patches and brief behavioral counseling.

Overall, 21.3% successfully quit. Several factors predicted success: being male, age 40 or older, living with a partner, high motivation, and concern about weight gain. But marijuana use emerged as one of the most powerful negative predictors.

Smokers who also used marijuana had an adjusted odds ratio of 0.4 for quitting, meaning they were roughly half as likely to succeed compared to non-marijuana users. Having other smokers in the household also reduced success (odds ratio 0.8).

Another striking finding: 96% of participants who smoked three or more cigarettes in the first four weeks of treatment eventually relapsed to regular smoking, making early lapse the strongest predictor of long-term failure.

Why it matters

This is one of the few large studies to identify marijuana use as a specific barrier to tobacco cessation. For the millions of people who use both substances, this finding suggests that addressing cannabis use may be important for successful tobacco quitting.

The numbers in context

1,481 subjects. Mean 32 cigarettes/day. 21.3% quit rate at 26 weeks. Marijuana use odds ratio: 0.4 (half the chance of quitting). 96% of those smoking 3+ cigarettes in the first 4 weeks relapsed.

How the study worked

Prospective cohort study of 1,481 subjects recruited by media who smoked 15+ cigarettes per day. Twelve weeks of transdermal nicotine with monthly behavioral counseling. Outcome: sustained cessation for 28 days before week-26 visit, verified by expired carbon monoxide. Logistic regression identified predictors.

What this study cannot tell us

Marijuana use was self-reported and not the primary study outcome. The study did not control for the type, frequency, or quantity of marijuana use. It cannot determine whether marijuana use causally impeded quitting or was a marker for other factors (impulsivity, higher addiction severity) that predicted failure.

How to read the evidence

A large prospective study with biochemically verified outcomes and multivariate analysis. Strong design, though marijuana use was not the primary variable of interest.

When this study was published

Published in 1994. Modern smoking cessation includes additional pharmacotherapies (varenicline, bupropion) not available at the time.

The bigger picture

The relationship between cannabis and tobacco use is bidirectional and complex. This study identified cannabis as a barrier to tobacco cessation, adding to evidence that the two substances interact in ways that complicate quitting either one.

Questions still open

Does cannabis interfere with nicotine cessation through biological mechanisms (shared reward pathways) or behavioral ones (triggering smoking habits)? Would addressing cannabis use alongside tobacco improve quit rates? Do people who mix cannabis and tobacco in joints have even worse outcomes?

Common questions

Does cannabis make it harder to quit cigarettes?

In this study, marijuana users were about half as likely to successfully quit tobacco compared to non-users. The mechanism (biological vs. behavioral) was not determined.

What was the overall quit rate?

21.3% of participants achieved sustained cessation at 26 weeks, verified by carbon monoxide testing.

Read the original research

Prospective study of factors predicting outcome of transdermal nicotine treatment in smoking cessation.

BMJ (Clinical research ed.), 309(6958), 842-6

View on PubMed ↗

Citation

Gourlay, S G; Forbes, A; Marriner, T; Pethica, D; McNeil, J J. (1994). Prospective study of factors predicting outcome of transdermal nicotine treatment in smoking cessation.. BMJ (Clinical research ed.), 309(6958), 842-6.