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Marijuana Use Cut the Odds of Successfully Quitting Tobacco in Half

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.

Gourlay, S G et al.·BMJ (Clinical research ed.)·1994·Moderate EvidenceProspective Cohort
Quitting (221)Addiction (1380)
RTHC-00049Prospective CohortModerate Evidence1994RETHINKTHC RESEARCH DATABASErethinkthc.com/research

Quick Facts

Study Type
Prospective Cohort
Evidence
Moderate Evidence
Sample
N=1,481

What This Study 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.

Key Numbers

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 They Did This

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.

Why This Research 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 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.

What This Study Doesn't 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.

Questions This Raises

  • ?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?

Trust & Context

Key Stat:
Marijuana users had half the odds of successfully quitting tobacco
Evidence Grade:
A large prospective study with biochemically verified outcomes and multivariate analysis. Strong design, though marijuana use was not the primary variable of interest.
Study Age:
Published in 1994. Modern smoking cessation includes additional pharmacotherapies (varenicline, bupropion) not available at the time.
Original Title:
Prospective study of factors predicting outcome of transdermal nicotine treatment in smoking cessation.
Published In:
BMJ (Clinical research ed.), 309(6958), 842-6 (1994)
Database ID:
RTHC-00049

Evidence Hierarchy

Meta-Analysis / Systematic Review
Randomized Controlled Trial
Cohort / Case-ControlFollows or compares groups over time
This study
Cross-Sectional / Observational
Case Report / Animal Study

Enrolls participants and follows them forward in time.

What do these levels mean? →

Frequently Asked 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 More on RethinkTHC

Cite This Study

RTHC-00049·https://rethinkthc.com/research/RTHC-00049

APA

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.

MLA

Gourlay, S G, et al. "Prospective study of factors predicting outcome of transdermal nicotine treatment in smoking cessation.." BMJ (Clinical research ed.), 1994.

RethinkTHC

RethinkTHC Research Database. "Prospective study of factors predicting outcome of transderm..." RTHC-00049. Retrieved from https://rethinkthc.com/research/gourlay-1994-prospective-study-of-factors

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Study data sourced from PubMed, a service of the U.S. National Library of Medicine, National Institutes of Health.

This study breakdown was produced by the RethinkTHC research team. We analyze and report published research findings without making health recommendations. All interpretations are based solely on the published abstract and study data.

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