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SAN DIEGO (KSWB/KUSI) — Teens and young adults who use cannabis may be significantly more likely to become regular tobacco users later on, according to new research led by the University of California, San Diego.
The study, published this week in the journal Tobacco Control, found that cannabis use among youth may be responsible for roughly 13 percent of new cases of regular tobacco use in the U.S.
“This study challenges long-held assumptions about the pathways between cannabis and tobacco use among youth,” said corresponding study author Karen Messer, Ph.D., professor at the UC San Diego Herbert Wertheim School of Public Health and Human Longevity Science and director of biostatistics at UC San Diego Moores Cancer Center.
Researchers in 2017 analyzed national data from more than 13,800 respondents between the ages of 12 and 24 who had not previously been regular tobacco users. Among those surveyed, 15 percent reported using cannabis within the previous year. Four years later, cannabis users were significantly more likely to have taken up regular tobacco use compared to non-users.
“These findings underscore the importance of investigating not only the direct effects of cannabis, but also its broader influence on patterns of tobacco initiation and dependence,” Messer explained.
Among the younger respondents, age 12 to 17, 32.7 percent of those who used cannabis had become regular tobacco users by 2021, about 15 percentage points higher than their peers who did not use cannabis. For young adults, age 18 to 24, the difference was smaller but still notable, with 14 percent of cannabis users becoming regular tobacco users.
When weighed on a national level, researchers estimate that more than 500,000 fewer young Americans might have avoided regular tobacco use if they had not previously used cannabis.
The observational study does not prove that cannabis directly causes tobacco use, but it does highlight an emerging “reverse gateway” effect, suggesting that using cannabis may lead to the initiation of other addictive substances like tobacco.
Researchers noted that additional factors such as peer influences, socioeconomic status and general susceptibility to substance use were not fully accounted for and could play a role.
Still, the authors conclude that cannabis use among youth should be considered a major risk factor for later tobacco addiction. They say prevention efforts should address both substances together.
The research was conducted by scientists at the UC San Diego Herbert Wertheim School of Public Health and Human Longevity Science. It was funded in part by the Tobacco-Related Disease Research Program of the University of California and the National Cancer Institute.
The full study is available online at Tobacco Control.
