Cannabis and nicotine co-use is widespread among young adults

Simultaneous use of cannabis with nicotine and tobacco products is common among cannabis users-particularly those who vape-according to a new study from Columbia University Mailman School of Public Health. The research also shows that both vaped and smoked cannabis use have increased over time, with more participants initiating use than quitting. Until now, the frequency, patterns, and motivations for cannabis use in early adulthood have remained understudied. The findings are published in Tobacco Induced Diseases.

The study reveals that young adults in the New York City area-including those who do not vape or smoke nicotine-use multiple forms of cannabis, such as vapes, edibles, and topicals. Cannabis is the third most commonly used drug worldwide. In 2023, an estimated 61.8 million people -- 22 percent of Americans ages 12 and older -- reported using marijuana at least once in the past year.

"Cannabis use in the U.S. represents a multifaceted and evolving public health challenge that has, for too long, been overlooked," said Katlyn McGraw, PhD, postdoctoral research scientist of Environmental Health Sciences at Columbia Mailman School. "We aimed to better understand use patterns and potential exposure to cannabis-related contaminants and associated health effects. Our findings show that cannabis use is diverse, complex, and growing -underscoring the need for further investigation."

To examine trends in cannabis use and product types, the research team analyzed data from the VapeScan longitudinal study, designed to evaluate subclinical health effects of e-cigarette use. The cohort included 372 adults ages 18–50 in the New York City region assessed between 2021 and 2024, regardless of cannabis use status.

Participants were evaluated at three time points: baseline (visit 1), approximately 12 months later (visit 2), and approximately 24 months later (visit 3). At the first visit, respondents completed questions about cannabis use. A more detailed questionnaire administered at visit 2 assessed longitudinal trends and specific methods of use. Participants were categorized as exclusive cannabis users, exclusive e-cigarette users, non–substance users, or dual users -- those reporting daily or some-day use of both e-cigarettes and cigarettes.

At visit 1:

• 34% reported dual substance use
• 4% reported exclusive cannabis use
• 35% reported e-cigarette use without cannabis
• 28% reported no substance use

By visit 2, 59% of participants reported cannabis use:

• 29% vaped cannabis
• 28% smoked cannabis
• 51% consumed edibles
• 32% used CBD products
• 4% used topical cannabis

Frequency and intensity differed by product type. Importantly, self-reported vaped or smoked cannabis use changed between visits: 21 percent of participants were new users at visit 2, while only 6 percent of those who vaped or smoked at visit 1 had quit. Rates of dual cannabis/e-cigarette use were similar between men and women.

"Frequent cannabis use is becoming more widespread and will likely continue to rise with changing social norms, policy liberalization, and the increasing availability and promotion of cannabis products," McGraw noted. "The prevalence of cannabis use among teens and young adults is increasing, as is the variety of products-edibles, concentrates, vapes-adding to the complexity of studying health effects.

"As the third most widely used drug globally, understanding the health implications of cannabis is essential," says Ana Navas-Acien, MD, PhD, Columbia Mailman School Leon Hess Professor and Chair, Environmental Health Sciences.."Our study highlights the importance of assessing cannabis exposure, including potential contaminants, and underscores that cannabis use is multifaceted. Regulatory policies and shifting consumer preferences further complicate efforts to accurately characterize exposure. Strengthening public health education that informs young adults about the compounded risks of cannabis–nicotine co-use is a first step."

Co-authors include Nancy LoIacono, Siyue Gao, William Anderson, Dona Sangapalaarachchi, Vesna Illievski, Justin Liu, Silvia Martins, and Tiffany R. Sanchez, Columbia Mailman School of Public Health; and Elizabeth Oelsner and Daichi Shimbo, Columbia University Irving Medical Center.