Cannabis smoking did not prevent people from quitting cigarettes in a large cancer society study

Among 4,535 cigarette smokers followed for about 3 years, cannabis smoking status had no significant effect on rates of quitting cigarettes, regardless of how frequently cannabis was used.

Westmaas, J Lee et al.·Cancer epidemiology·2021·Moderate EvidenceLongitudinal Cohort
RTHC-03611Longitudinal CohortModerate Evidence2021RETHINKTHC RESEARCH DATABASErethinkthc.com/research

Quick Facts

Study Type
Longitudinal Cohort
Evidence
Moderate Evidence
Sample
N=4,535

What This Study Found

Adjusted cigarette quitting rates did not differ by cannabis status: never cannabis users (36.2%), former users (34.1%), and recent users (33.6%). Among recent cannabis smokers, quitting rates were similar across low (31.4%), moderate (36.7%), and high frequency (34.4%) use groups.

Key Numbers

Sample: 4,535 smokers. Follow-up: 3.1 years average. Quit rates: never cannabis 36.2%, former 34.1%, recent 33.6%. By frequency: low 31.4%, moderate 36.7%, high 34.4%. Intention to quit in 30 days: no difference (p=0.83).

How They Did This

Longitudinal study of 4,535 adult cigarette smokers from the American Cancer Society Cancer Prevention Study-3, enrolled 2009-2013 with follow-up in 2015-2017 (mean 3.1 years). Cannabis status was retrospectively assessed at baseline. Models adjusted for sociodemographics, smoking behaviors, and health factors.

Why This Research Matters

As cannabis use increases, clinicians have worried it might make cigarette cessation harder. This large, well-designed study found no evidence supporting that concern.

The Bigger Picture

The lack of association between cannabis use and cigarette cessation suggests clinicians can address each substance independently rather than assuming one prevents quitting the other.

What This Study Doesn't Tell Us

Self-reported cannabis and cigarette use. Retrospective cannabis status assessment. Follow-up was about 3 years; longer-term effects are unknown. Participants in a cancer prevention study may not be representative.

Questions This Raises

  • ?Does the mode of cannabis consumption matter (smoking vs. edibles) for cigarette cessation outcomes?
  • ?Would results differ in populations with more heavy cannabis use?

Trust & Context

Key Stat:
No significant difference in cigarette quit rates regardless of cannabis use status
Evidence Grade:
Large cohort with longitudinal design and appropriate adjustments, though self-reported measures limit precision.
Study Age:
Published in 2021 with follow-up from 2009-2017.
Original Title:
Association between Smoking Cannabis and Quitting Cigarettes in a Large American Cancer Society Cohort.
Published In:
Cancer epidemiology, biomarkers & prevention : a publication of the American Association for Cancer Research, cosponsored by the American Society of Preventive Oncology, 30(10), 1956-1964 (2021)
Database ID:
RTHC-03611

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

Follows a group of people over time to track how outcomes develop.

What do these levels mean? →

Frequently Asked Questions

Does smoking cannabis make it harder to quit cigarettes?

This study of over 4,500 smokers found no evidence of that. Cigarette quit rates were similar whether participants never used cannabis, formerly used it, or currently used it.

Did heavier cannabis use matter?

No. Among recent cannabis smokers, quit rates were similar whether they used cannabis 3 days a month or 20+ days a month.

Read More on RethinkTHC

Cite This Study

RTHC-03611·https://rethinkthc.com/research/RTHC-03611

APA

Westmaas, J Lee; Strollo, Sara E; Newton, Christina C; Carter, Brian D; Diver, W Ryan; Flanders, W Dana; Stevens, Victoria L; Patel, Alpa V; Alcaraz, Kassandra I; Thrul, Johannes; Jacobs, Eric J. (2021). Association between Smoking Cannabis and Quitting Cigarettes in a Large American Cancer Society Cohort.. Cancer epidemiology, biomarkers & prevention : a publication of the American Association for Cancer Research, cosponsored by the American Society of Preventive Oncology, 30(10), 1956-1964. https://doi.org/10.1158/1055-9965.EPI-20-1810

MLA

Westmaas, J Lee, et al. "Association between Smoking Cannabis and Quitting Cigarettes in a Large American Cancer Society Cohort.." Cancer epidemiology, 2021. https://doi.org/10.1158/1055-9965.EPI-20-1810

RethinkTHC

RethinkTHC Research Database. "Association between Smoking Cannabis and Quitting Cigarettes..." RTHC-03611. Retrieved from https://rethinkthc.com/research/westmaas-2021-association-between-smoking-cannabis

Access the Original Study

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.