A recent study published in PloS One has revealed that individuals who use both tobacco and cannabis are at a heightened risk of reporting anxiety and depression compared to non-users.
Dr. Nhung Nguyen, an assistant professor of medicine at the University of California, San Francisco School of Medicine, highlighted that previous research primarily focused on the association between mental health and the use of either tobacco or cannabis. However, she emphasized that many people who use tobacco also use cannabis, and vice versa.
Dr. Nguyen explained, “If we only address the use of a single substance in relation to mental health, we might miss opportunities to address multiple substance-use issues simultaneously, potentially resulting in less effective treatment.”
To investigate the connections between mental health and co-use of these substances, researchers analyzed data collected between 2020 and 2022 from 53,843 adults who participated in the online cohort COVID-19 Citizen Study. The participants, with a mean age of 51 years and 67.9% being women, were divided into four groups: tobacco-only users (4.9%), cannabis-only users (6.9%), co-users (1.6%), and non-users (86.6%).
The study’s findings revealed that co-users reported the highest proportions of anxiety (26.5%) and depression (28.3%) compared to all other groups. In contrast, non-users reported the lowest proportions, with 10.6% reporting anxiety and 11.2% reporting depression.
When compared to non-users, co-users had adjusted odds ratios (ORs) of 1.89 for anxiety (95% CI, 1.64-2.18) and 1.77 for depression (95% CI, 1.46-2.16). Dr. Nguyen noted a graded effect size, indicating that the odds of mental health disorders increased progressively from non-use to tobacco-only use, cannabis-only use, and co-use.
Furthermore, the researchers found that compared to tobacco-only use, co-use (OR = 1.35; 95% CI, 1.08-1.69) and cannabis-only use (OR = 1.17; 95% CI, 1.00-1.37) were associated with higher adjusted odds for anxiety but not depression.
Dr. Nguyen emphasized that more research is necessary to determine whether individuals with mental health disorders are more prone to using tobacco and cannabis or whether the use of these substances contributes to the development of mental health disorders. She suggested that the relationship between tobacco, cannabis use, and mental health is complex, with growing evidence supporting a bidirectional relationship.
Ultimately, Dr. Nguyen suggested that coordinating tobacco and cannabis cessation with mental health treatment may benefit individuals who co-use these substances. Additionally, she recommended implementing screening for tobacco and cannabis use in mental health treatment settings to identify and support those at risk.
