Tobacco and cannabis co-users at greater risk for mental health disorders

Key takeaways:

• Among co-users, 26.5% and 28.3% reported anxiety and depression, respectively.
• Coordination of tobacco and cannabis cessation with mental health treatment may be beneficial for co-users.

Users of both tobacco and cannabis were more likely than nonusers to report anxiety and depression, a recent study in PloS One showed.

“Previous research mostly examined the association between mental health with use of either tobacco or cannabis,” Nhung Nguyen, PhD, an assistant professor of medicine at the University of California, San Francisco School of Medicine, told Healio.

However, Nguyen noted people who use tobacco “often use cannabis and vice versa.”

“If we only address use of a single substance with mental health, we might miss opportunities to address multiple substance-use issues simultaneously, potentially resulting into less effective treatment,” she explained.

To assess mental health links among co-users, the researchers evaluated 2020 to 2022 data from 53,843 adults, taken from the online cohort COVID-19 Citizen Study.

Participants had a mean age of 51 years, and 67.9% were women. Among the sample, 4.9% reported tobacco-only use, 6.9% reported cannabis-only use, 1.6% reported co-use and 86.6% reported nonuse.
Nguyen and colleagues found that 26.5% and 28.3% of co-users reported anxiety and depression, respectively — the highest proportions among all groups.

The lowest proportions were found in nonusers, of whom 10.6% reported anxiety and 11.2% reported depression.

Compared with nonusers, the adjusted ORs for mental health disorders among co-users were 1.89 (95% CI, 1.64-2.18) for anxiety and 1.77 (95% CI, 1.46-2.16) for depression.

“I found a graded effect size, [with] the odds of mental health disorders ranging from lowest for nonuse, tobacco-only, cannabis-only, to highest for co-use — very interesting,” Nguyen said. “This finding suggests both independent effects of tobacco and cannabis and joint effects of both substances on mental health.”

The researchers also noted that compared with tobacco-only use, co-use (OR = 1.35; 95% CI, 1.08-1.69) and cannabis-only use (OR = 1.17; 95% CI, 1-1.37) were associated with higher adjusted odds for anxiety but not depression.

Nguyen said more research is needed is determine whether individuals with mental health disorders are more inclined to smoke and use cannabis, as opposed to smoking and cannabis being the underlying cause of disorders.

“The relationship between use of tobacco and cannabis and mental health is complex, and accumulating evidence supports a bidirectional relationship,” she said.

Ultimately, “coordinating tobacco and cannabis cessation with mental health treatment may be beneficial for people with co-use of tobacco and cannabis,” Nguyen said. “In addition, screening for use of tobacco and cannabis should be implemented in mental health treatment settings.”