(HealthDay News) – Half of young adult tobacco smokers also have used marijuana in the last 30 days, and co-use occurs on nearly half of the days either substance is used.

Danielle E. Ramo, PhD, and Judith J. Prochaska, PhD, MPH, from the University of California at San Francisco, recruited young adults (age 18–25) who had smoked at least one cigarette in the past 30 days to participate in an online survey to examine marijuana use.

Of the 1,808 smokers who completed the survey, the researchers found that more than half of the participants (53%) reported past-month marijuana use, with a median use reported as 18 out of the past 30 days. On almost half of the days on which either substance was used, co-use was reported (45.5%). Co-use of tobacco and marijuana was more frequent among Caucasians, participants living in the Northeast or in rural areas, in nonstudents versus students, and in daily smokers. Co-use or prevalence of marijuana use was not linked to residence in a state with legalized medical marijuana, nor to age or household income.

“These results indicate a higher prevalence of marijuana use and co-use of tobacco in young adult smokers than is reported in nationally representative surveys,” the authors write. “Cessation treatments for young adult smokers should consider broadening intervention targets to include marijuana.”

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