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expert reaction to study looking at e-cigarette use and marijuana use in young people

Research, published in JAMA Pediatrics, reports that adolescents who have a history of using e-cigarettes are more likely to use marijuana.


Prof Linda Bauld, Professor of Public Health, University of Edinburgh, said:

“This review of existing studies finds that young people who try e-cigarettes may be more likely to try marijuana, and in some cases experimentation with e-cigarettes comes first.  This doesn’t prove that vaping is causing marijuana use but instead highlights something we have known for many years – that young people who are more prone to risky behaviours may try several different substances before they are legally permitted to do so.  Although the paper didn’t assess alcohol or other drug use, other research has found that young people who vape are also more likely to have tried alcohol, and that young people who use marijuana are also more likely to try other illegal drugs.

“Context is also important, as the authors point out.  The vast majority of the studies in the review are from North America and were conducted in a period where marijuana use was rising and attitudes towards cannabis were softening in the context of legalisation for recreational use.  No relevant UK studies were identified, and only four from Europe, all of which found weaker associations between vaping and marijuana use.  This is not surprising as stricter policies are in place in European countries than North America for both e-cigarettes and marijuana.”


Prof Peter Hajek, Director of the Tobacco Dependence Research Unit, Queen Mary University of London, said:

“The study conclusion claims that the findings show that vaping somehow causes marijuana use.  In fact, the study only found that, unsurprisingly, the same adolescents who experiment with one drug also experiment with the other, and this happens in any order.”


Dr Sarah Jackson, Senior Research Fellow, UCL Tobacco and Alcohol Research Group, UCL, said:

“This appears to be a robust review of observational studies that have looked at the relationship between use of e-cigarettes and use of marijuana among young people.  The results show that young people who use e-cigarettes tend to be more likely to use marijuana than those who do not use e-cigarettes, with some evidence that e-cigarette use precedes marijuana use.  The authors suggest there may potentially be effects of e-cigarette use on the brain that may increase the likelihood of other substance use, so they suggest there may be a causal role of e-cigarettes in subsequent marijuana use – however, an alternative explanation is that the association may be driven by young people with a greater propensity to try one product (for example, those who are more rebellious, impulsive, or sensation-seeking) also being likely to try the other.  This is consistent with wider literature documenting clustering of risky behaviours within individuals, and with this study’s finding that the association between e-cigarette use and marijuana use was stronger among young people who also smoked cigarettes.  The authors’ conclusion that their findings “highlight the importance of addressing the rapid increases in e-cigarette use among youths as a means to help limit marijuana use” overstates the data in assuming a causal association exists.”


Prof John Britton, Director of the UK Centre for Tobacco & Alcohol Studies, University of Nottingham, said:

“This paper reports an entirely predictable finding, that young people who use one inhaled drug are more likely to use another.  The finding is unsurprising because marijuana is often smoked with tobacco, and tobacco smokers are more likely to use e-cigarettes.  The study does not however provide any evidence that an association between e-cigarette and cannabis use is causal.”


‘Association between electronic cigarette use and marijuana use among adolescents and young adults’ by Nicholas Chadi et al. was published in JAMA Pediatrics at 16:00 UK time on Monday 12 August 2019. 

DOI: 10.1001/jamapediatrics.2019.2574


Declared interests

Prof Linda Bauld: “Prof Bauld is CRUK/BUPA Chair in Behavioural Research for Cancer Prevention, Cancer Research UK; Deputy Director, UK Centre for Tobacco and Alcohol Studies; and Honorary Professor, University of Stirling.”

Prof Peter Hajek: “No conflicts.”

Dr Sarah Jackson: “I have no conflicts of interest to declare.”

None others received.

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