Teenagers and young adults who use cannabis have a higher risk of progressing to regular tobacco use, study finds

Teens and young adults who use cannabis are more likely to become regular tobacco users—even if they haven’t previously tried tobacco—compared to similar people who do not use cannabis, suggests a US study published online in the journal Tobacco Control.

Around 13% of new onset tobacco use was estimated to be attributable to cannabis, the study found.

Tobacco smoking has been considered a gateway to cannabis use since the 1970s, when smoking was much more prevalent and when almost all people who used cannabis had smoked tobacco first.

Although tobacco use among teens and young adults has declined considerably in the United States since the 1970s, cannabis use has not. This raises the question of whether a reverse gateway from cannabis to regular tobacco use might exist.

To investigate, the authors mined data from a regular survey of US households called PATH (Population Assessment of Tobacco and Health) to look at the association of cannabis use by teens and young adults in 2017 and their likelihood of regular tobacco use four years later in 2021.

A total of 13,851 respondents aged 12–24 years who, in 2017, had said they had never or never regularly used any form of tobacco (combustible or non-combustible) and who completed the subsequent surveys were identified, of which 15.4% had admitted using cannabis in the last 12 months. The likelihood of cannabis use increased with the age of the respondent.

Each person who used cannabis was matched to a similar non-user according to a number of characteristics including demographics, history of experimentation with tobacco products, perceived harmfulness of cigarettes and mental health symptoms.

The study found that 32.7% of US teens aged 12–17 years who had used cannabis had progressed to regular tobacco use four years later—an increase of 15.6 percentage points compared with their matched controls.

Among the young adults aged 18–24 years, 14% of those who used cannabis reported regular tobacco use—an increase of 5.4 percentage points over their matched controls.

The analysis attributed 13% of total new regular tobacco use to cannabis and when extrapolated across the entire US population, the authors estimated that 509,800 fewer US teens and young adults would have progressed to regular tobacco use in 2021 if they had not had previous experience of cannabis in 2017.

This is an observational study, and as such, can’t establish cause and effect, and the authors also acknowledge several limitations including the use of self-reported measures for tobacco and cannabis use.

Although a comprehensive list of baseline covariates was considered, some factors such as peer influences, socioeconomic factors and an underlying liability to substance use may not have been captured fully. Assessing cannabis use in the past 12 months rather than current use is also likely to have attenuated the estimated effect size.

Nevertheless, the authors conclude that cannabis use by US youth is a major risk factor for progression to regular tobacco use, independent of whether or not they have yet tried tobacco.

“The finding that prior cannabis use is a major risk factor for initiation of current regular tobacco use among youth, independent of whether or not they have tried tobacco, suggests that cannabis prevention should be included as a key goal in tobacco control programs,” the authors said.

“While early cannabis use is seen as a major public health problem, none of the major health agencies have addressed the potential of early cannabis use to increase future regular tobacco use.”

They add, “This study provides evidence that failure to address cannabis use among young people has the potential to undermine the progress tobacco control efforts have made in reducing tobacco initiation and progression to regular use.”