Published in the Psychology of Addictive Behaviours review, the study is based on a survey carried out in 2017 and 2018 of a group of 2400 young adults in California, who answered questions about their use of cannabis, tobacco or nicotine and their use of both substances at the same time.
“There is growing concern that as more states legalise marijuana, there also will be an increase in tobacco use because the two substances may be used together.
Co-use of cannabis and tobacco could reverse some of the progress made on reducing rates of tobacco use,” said Joan Tucker, lead author of the study and a behavioural specialist at non-profit research institute RAND.
Almost half of the participants in the survey stated they had used cannabis in 2018.
43% had consumed tobacco or nicotine the same year. Around 37% stated they had used the two substances together at some point in the previous 12 months.
Over 80% of the survey participants who stated they had used marijuana had also used tobacco in 2018.
Among these, 17% had used these substances one after the other and 14% had used them together, in the same device.
Combining the two substances increases risk
The survey revealed that concomitant consumption of cannabis and tobacco was linked to poor mental and physical health in young people, as well as behavioural issues such as self-harm, truanting, suspension from schools or involvement with the police.
People who smoked tobacco and marijuana in the same period, but separately, presented no higher a risk than people who consumed only one of these substances.
“How these products are used together matters in terms of potential health consequences and functioning among people in their late teens and early 20s.
“Our findings suggest that we can no longer just think about the consequences of tobacco use or marijuana use alone-we have to think about them together, concluded Tucker.
In the United States, national data shows that young adults aged 18 to 25 are more likely to consume cannabis, tobacco, or nicotine-based products than any other age group.