Cannabis and Tobacco Co-use Study

The purpose of this study is to better understand tobacco outcomes using a well-known stop smoking medication, varenicline, and financial incentives with tobacco users. The investigators are also interested in how cannabis/marijuana and tobacco interact during a tobacco quit attempt. All participants will receive tobacco cessation treatment (varenicline) for 12 weeks. This study will recruit adult tobacco users (ages 18-40) who are motivated to quit smoking cigarettes.

Cannabis co-use among tobacco users is exceedingly common and rates of co-use appear to be increasing among adults in the US, which is consistent with overall increases in cannabis use rates among US adults. Given the current cannabis landscape, further increases in cannabis use are likely and may result in continued increases in the co-use of cannabis and tobacco.

Despite high rates of co-use, there is little consensus regarding treatment recommendations for this population and an understanding of the impact of co-use on successful cessation. The literature on the impact of co-use on tobacco cessation outcomes specifically has been mixed and fraught with limitations, including methodological variation, lack of biochemical verification to confirm cannabis use status and severity, and variations in study samples. Currently, no prospective studies have been conducted to evaluate the impact of cannabis use on tobacco cessation outcomes. Further, no studies have collected cannabis use changes during tobacco cessation treatment to assess for concurrent reductions, abstinence, or of greater concern, compensatory (i.e., increased) use as a result of tobacco reduction/abstinence.

This study is a prospective 12-week tobacco cessation trial using established methods and outcomes typical of tobacco cessation trials, but specifically recruiting co-users of cannabis. The aims of this proposed study are to; 1) examine the impact of cannabis co-use on tobacco cessation outcomes among co-users compared to tobacco only participants (Aim #1), 2) among cannabis co-users, assess changes in cannabis use during tobacco treatment (Aim #2), and 3) assess for a dose-dependent impact of cannabis co-use severity on tobacco cessation (Exploratory Aim #1).

Eligibility Criteria:
Inclusion Criteria:

1. Between the ages of 18 and 40 years old
2. Must be able to understand the study and provide written informed consent
3. Daily cigarette smoker for ≥ 6 months, smoking ≥ 5 cigarettes per day
4. Must submit a breath carbon monoxide (CO) sample of ≥ 7 parts per million (ppm) at the screening visit
5. Be interested in quitting smoking tobacco cigarettes (defined as a 5 or above on a 10-point Likert scale assessing interest in quitting \[1=not at all interested, 10=extremely interested\])
6. Must be willing to take varenicline for the standard 12-week course of treatment
7. If female, agreement to use birth control (any form) to avoid pregnancy during study procedures

   Additional inclusion criteria will be implemented for cannabis co-users, which include:
8. Self-reported use of cannabis on at least 10 out of the past 30 days or submit a positive qualitative urinary cannabinoid test at screening (limit of detection is 50 ng/ml)

Exclusion Criteria:

1. Any serious or unstable medical/psychiatric disorder (including severe substance use disorders, other than cannabis or tobacco use disorders) or other significant concern in the past three months that may interfere with study performance, impact participant safety, compliance with study procedures, or potentially confound the interpretation of findings
2. Currently pregnant, lactating, or contemplating pregnancy in the next 6 months
3. Current use of medications with smoking cessation efficacy
4. Use of any medications that would interfere with varenicline
5. No regular use of other tobacco or nicotine products other than combustible cigarettes (e.g., smokeless tobacco, electronic cigarettes, etc.) in the past month prior to the quit attempt