UW-CTRI Research Director Dr. Megan Piper and UW-CTRI Director Dr. Hasmeena Kathuria served on the American Thoracic Society expert panel who reviewed the latest evidence on co-use of cannabis and tobacco and made several important recommendations. Kathuria served as the chair, Piper as a co-chair.
“There’s a lot we don’t know about what happens when people use tobacco and cannabis,” Piper said. “The consensus from the panel was that we need to take several steps to better understand this co-use. First, as researchers, we need to adopt consistent terms and minimum data elements for all researchers to assess. Second, we need to study the prevalence of co-use among populations experiencing tobacco-related disparities. Third, there’s a clear need to evaluate how the use of cannabis impacts smoking cessation, including the medications people use to try to quit smoking, vaping or chewing nicotine. Finally, we agreed it’s wise to study the effects of co-use on the development and progression of lung diseases.”
While smoking cannabis is illegal in Wisconsin, many vendors and users get around that with a loophole in the law that allows the sale of synthetic cannabis products, including Delta-8.
“We didn’t find any data on the lung health effects of Delta-8 in the literature,” Kathuria said. “Given the growing availability and use of Delta-8, we need research to understand their health impacts, especially when inhaled alongside tobacco.”
Meanwhile, Wisconsin Rep. Bob Donovan (R) is seeking co-sponsorship for a bill that would close that loophole.
Piper said co-use seems to be expanding and can occur in several forms, including co-administration (blunts where people smoke both in the same product), sequential co-use (chasing one with the other), substitution or in an asynchronous manner.
The panel identified four priority topics for future study of smoking or vaping THC plus nicotine.
- Priority Topic #1: Common Data Elements and Terminology. What are the recommended and harmonized common terms related to tobacco and cannabis co-use that should be adopted to refer to: a) product types, b) co-use methods, c) patterns and d) reasons for co-use?
- Priority Topic #2: Characterization of co-use patterns and prevalence of co-use. What are the behavioral use patterns and prevalence of tobacco and cannabis co-use, overall and among populations that experience tobacco-related disparities?
- Priority Topic #3: Impact of Co-Use on Tobacco Cessation Outcomes. What is the impact of cannabis co-use on the effect of tobacco cessation pharmacotherapies and how do these tobacco cessation pharmacotherapies influence cannabis use? How does the reduction or cessation of cannabis use influence tobacco smoking/nicotine vaping cessation among people who co-use tobacco and cannabis?
- Priority Topic #4: Impact of Co-Use on Lung Health. What are the effects of inhaled tobacco and cannabis co-use on initiation and progression of lung disease (e.g., asthma, COPD, pulmonary fibrosis), including changes in pulmonary function, radiographic changes and pulmonary symptoms and how do these effects differ from use of only one product?
McClure EA, Piper ME, Crotty Alexander LE, Burnham EL, Freeman TP, Galiatsatos P, Lange AD, Lee DC, Leone FT, Melzer AC, Mermelstein J, Montgomery L, Rabin RA, Smith DM, St. Helen G, Weinberger AH, Kathuria H. (2025) Effects of Inhaled Tobacco and Cannabis Co-Use on Respiratory Health and Tobacco Cessation. An Official American Thoracic Society Research Statement. American Journal of Respiratory Critical Care Medicine. Online August 22, 2025.