Taking up vaping in adolescence or early adulthood is tied to a more than threefold hike in the odds of becoming a marijuana user, researchers report.
And the risk rose if people first tried vaping when relatively young, noted the research team led by Dr. Nicholas Chadi of Boston Children's Hospital.
"Odds of using marijuana in youth with e-cigarette use were higher in adolescents age 12 to 17 [more than four times the risk] than young adults age 18 to 24 years [a 40% higher risk]," Chadi and researchers reported Aug. 12 in the journal JAMA Pediatrics.
The link between vaping and pot smoke is alarming, experts say, since about 1 in every 3 U.S. high school students say they have vaped, and the increasing legalization of marijuana is making access so much easier for kids.
And as one expert not involved with the study said, there's another way vaping may make pot use easier for kids.
"Many of these vaping devices can be easily modified to allow users to experiment with other substances of abuse, including marijuana," noted Andrea Spatarella, from the Center for Tobacco Control at Northwell Health in Great Neck, N.Y.
Prior studies have also shown that exposing the "still-developing brain" to nicotine - whether from traditional cigarettes or vaping - "increases the risk [for] future substance abuse," she said.
In the new study, researchers sifted through data involving more than 128,000 people between the ages of 10 and 24.
Besides the finding that vaping was strongly tied to marijuana use, Chadi's group also found that use of e-cigarettes typically comes before the use of marijuana in the young - suggesting that the vaping habit is a "gateway" to the drug.
The Boston team also found that the vaping-pot connection was stronger in studies conducted after 2017 versus before. The reasons for that variation are unclear, the researchers said, but it could be linked to the recent and rapid uptake among kids of "small, high-technology types of [vaping devices] with refillable cartridges," such as the Juul e-cigarette.
And how might vaping encourage pot use?
According to Chadi and colleagues, the nicotine in e-cigarettes "may sensitize the reward and pleasure centers of the brain and increase the odds of using other forms of nicotine and other psychoactive substances (such as marijuana)."
That could be especially true in younger, still-developing brains, they said - helping to explain why the connection between vaping and pot use is so much stronger the earlier a vaping habit begins.
For all of these reasons - and the as-yet-unclear health effects of vaping itself - "nicotine use, especially during adolescence, should be discouraged," the researchers concluded.
Dr. Scott Krakower is assistant unit chief of psychiatry at Zucker Hillside Hospital in Glen Oaks, N.Y. Looking over the new findings, he said they counter the notion that vaping is "'non-harmful,' when in fact they often contain toxins and may lead to worsening smoking habits."
Now this new analysis suggests that e-cigarette use might raise young people's odds for pot-smoking, too, Krakower said. He believes that for this and other reasons, the U.S. federal government needs to enact tougher policies to help curb vaping among American youth.