By Lisa Rapaport
Adolescents and young adults who have smoked e-cigarettes are more than three times more likely to move on to marijuana than youth who never try vaping, a research review study suggests.
Researchers examined data from 21 previously published studies with more than 128,000 participants ages 10 to 24. Overall, young people who used e-cigarettes were 3.5 times more likely to use marijuana, the analysis found.
Teen vapers were most at risk for marijuana use. Among adolescents ages12 to 17, e-cigarette users were 4.3 times more likely to use marijuana. Among young adults ages 18 to 24, vapers were 2.3 times more likely to use marijuana.
"E-cigarettes are often considered benign or harmless by youth and their families," said Dr. Nicholas Chadi, lead author of the study and an assistant professor of pediatrics at Sainte-Justine University Hospital at the University of Montreal in Canada.
"What this study suggests is that e-cigarettes (most of which contain nicotine) should be considered harmful, in a similar way as other substances like alcohol and tobacco, which have also been associated with increased marijuana use," Chadi said by email.
While teen smoking has long been linked to an increased risk of drug use, U.S. adolescents today are more apt to try vaping than smoking traditional cigarettes - and less is known about how e-cigarettes impact future substance use.
Big tobacco companies are all developing e-cigarettes. The battery-powered devices feature a glowing tip and a heating element that turns liquid nicotine and other flavorings into a cloud of vapor that users inhale.
The rise of vaping is problematic in part because most people with substance use disorders develop these problems before they turn 18, researchers noted August 12 online in JAMA Pediatrics. And adolescents whose brains are still developing are more vulnerable than older adults to the addictive properties of nicotine, alcohol, marijuana and other drugs.
In the current analysis, the connection between vaping and marijuana use was stronger for North American young people and for the past two years than for earlier studies or research with participants in Europe or other places.
Vaping in combination with smoking traditional cigarettes was also more strongly connected to marijuana use than vaping alone.
None of the smaller studies in the analysis were controlled experiments, so they could not prove that vaping directly impacts marijuana use. Researchers also didn't examine the health outcomes associated with vaping.
Another limitation of the study is that researchers looked at all marijuana use - whether it was trying a single joint one time at a party ages ago or an ongoing daily habit - so it wasn't possible to see how vaping might impact the frequency of marijuana use.
Even so, it's possible that experimenting with e-cigarettes might make young people more curious about marijuana, reduce perceived harm of marijuana use, and increase the social access to marijuana from peers and friends, said Hongying Dai, a public health researcher at the University of Nebraska Medical Center in Omaha who wasn't involved in the study.
"The brain is still in development during the teen years and is not mature for young adults, nicotine exposure might lead to changes in the central nervous system that predisposes teens and young adults to dependence on other drugs of abuse," Dai said by email.
And, vaping might also lead to more dangerous substance use problems than smoking traditional cigarettes, Dai added.
"One difference between e-cigarettes and traditional cigarettes is that adolescents and young adults who experiment with e-cigarettes may use the same device or switch to newer generation devices for vaping marijuana, which could lead to use of substance with stronger addictive effects," Dai said.
JAMA Pediatrics 2019.
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