A 'Joint' Problem

Investigating marijuana and tobacco co-use and its impacts on smoking cessation

by Callan Frye

Tobacco isn’t the only thing being smoked in the Deep South, and for many, it’s only half of their habit.

Marijuana, long thought to be a gateway to harder substances, turns out to be popular among cigarette smokers, with rates of co-use of the two substances increasing among adults from 2003 to 2012. Researchers don’t yet know how much of a problem that poses for people trying to quit tobacco.

To learn more, a team of addiction investigators at the Medical University of South Carolina (MUSC), led by Erin A. McClure, Ph.D., assistant professor in the Department of Psychiatry and Behavioral Sciences, conducted an online survey of smoking habits among individuals who had used both marijuana and tobacco within a 30-day period. The survey results were published in Addictive Behaviors in March 2019.

The MUSC team found that more participants used marijuana and tobacco sequentially than simultaneously. For example, more participants used a tobacco cigarette as a “chaser” to marijuana than smoked joints containing both marijuana and tobacco, called spliffs.

The study also found that the degree to which marijuana and tobacco usage was interrelated differed greatly by user. Twenty-six percent of users reported that they had smoked most of their cigarettes around the time that they were using marijuana or were high. Compared to those who smoked the two substances individually, these co-users were more likely to have a greater tobacco dependence and to smoke more cigarettes per day.

“So if somebody’s trying to quit smoking cigarettes but they always use marijuana and tobacco together, it’s probably going to be much, much harder for them if they are still using marijuana than for somebody who uses both but their use is not related in any way,” says McClure.

The finding also raises the question of whether smoking tobacco after marijuana use enhances its subjective effects. It is possible that co-users of marijuana and tobacco who feel a more intense high because of the tobacco use are more likely to use them together. If this is the case, quitting cigarettes may be more difficult for these individuals, though this requires further study.

What is clear from the researchers’ findings is that everyone’s habit is a little different, and cessation programs will thus need to be personalized if they are to be effective.

McClure hopes to focus on tobacco cessation as she continues her research but also to identify people likely to struggle with quitting due to their marijuana use. She plans to further tailor treatment to these individuals to improve the success of their smoking cessation efforts.