Concurrent Use of Tobacco and Cannabis and Internalizing and Externalizing Problems in US Youths.

Importance: Little is known about whether concurrent use of tobacco and cannabis is associated with higher or lower levels of mental health problems than use of either substance alone among youths. Objective: To examine the association between concurrent use of tobacco and cannabis and mental health problems in a national sample of US youths. Design, Setting, and Participants: This cross-sectional study analyzed publicly available wave 6 data within the Population Assessment of Tobacco and Health (PATH) Study, a nationally representative cohort study of US youths aged 14 to 17 years, collected from March to November 2021. This analysis used wave 6 single-wave weights to obtain statistically valid estimates for cross-sectional analyses generalizable to the wave 4 cohort sample. Data were analyzed from November 15, 2023, to April 20, 2024. Exposure: Past 30-day use of any tobacco and cannabis products was self-reported and categorized into 4 exclusive patterns: concurrent, tobacco only, cannabis only, and nonuse. Main Outcomes and Measures: Self-reported past-year internalizing and externalizing mental health problems were measured using the modified version of the Global Appraisal of Individual Needs-Short Screener and separately categorized into 3 levels: low (0-1 symptoms), moderate (2-3 symptoms), and high (≥4 symptoms). Results: A total of 5585 youths were included in the study, with a weighted proportion of 51.3% being male and 72.5% aged 15 to 17 years. In terms of race and ethnicity, 1606 youths (25.7%) were Hispanic, 626 (12.7%) were non-Hispanic Black, 2481 (50.5%) were non-Hispanic White, and 555 (11.0%) were non-Hispanic other. The prevalence of concurrent use (3.4% [95% CI, 2.9%-4.0%]) was comparable to tobacco-only use (3.9% [95% CI, 3.2%-4.6%]), but greater than cannabis-only use (2.5% [95% CI, 2.1%-2.9%]). High levels of internalizing and externalizing problems were most common for the concurrent use group (internalizing: 47.4% [95% CI, 39.2%-55.9%]; externalizing: 61.6% [95% CI, 54.1%-68.7%]), followed by the cannabis-only use group (internalizing: 44.8% [95% CI, 35.7%-54.1%]; externalizing: 48.5% [95% CI, 39.1%-57.9%]), the tobacco-only use group (internalizing: 41.4% [95% CI, 33.7%-49.5%]; externalizing: 46.3% [95% CI, 38.3%-54.5%]), and the nonuse group (internalizing: 22.4% [95% CI, 21.1%-23.8%]; externalizing: 30.4% [95% CI, 28.9%-31.9%]). After controlling for covariates in ordinal logistic regression models, concurrent use of tobacco and cannabis was associated with greater odds of reporting higher levels of externalizing problems compared with tobacco-only use (adjusted odds ratio [AOR], 1.83 [95% CI, 1.15-2.91]) and cannabis-only use (AOR, 1.85 [95% CI, 1.11-3.06]). However, there were no statistically significant differences in the odds of internalizing problems between concurrent use and use of tobacco or cannabis alone. Conclusions and Relevance: In this cross-sectional study of the PATH Study wave 6 youth data, concurrent use of tobacco and cannabis was linked to higher levels of externalizing mental health problems than use of single substances, indicating a potential need to combine mental health support with tobacco and cannabis cessation interventions for youths.