Multivariable regression models comparing cigarette smoking–related variables and alcohol use between cigarette-only smokers and cigarette smokers who co-use cannabis, by presence versus absence of depressive symptoms*
| Outcome, weighted % | Co-use, depression | Co-use, no depression | Cigarette only, depression | Cigarette only, no depression | p value, main effect |
|---|---|---|---|---|---|
| Cigarette (nicotine) dependence | |||||
| Smoking frequency | |||||
| Daily smoking | 89.0 | 86.6 | 85.4 | 87.9 | 0.4 |
| Adjusted OR (95% CI) | 1.1 (0.8–1.7) | 0.9 (0.6–1.2) | 0.8 (0.6–1.1) | 1.00 | |
| Main effect, depressive symptoms | 0.7 | ||||
| Main effect, cannabis use | 0.7 | ||||
| Two-way interaction test: Depressive symptoms × cannabis use | 0.1 | ||||
| Cigarettes smoked per day | |||||
| ≤ 10 cigarettes | 50.2 | 52.6 | 49.3 | 51.1 | 0.9 |
| Adjusted OR (95% CI) | 1.0 (0.7–1.3) | 1.1 (0.8–1.4) | 0.9 (0.7–1.2) | 1.00 | |
| Main effect, depressive symptoms | 0.5 | ||||
| Main effect, cannabis use | 0.6 | ||||
| Two-way interaction test: Depressive symptoms × cannabis use | 0.9 | ||||
| Perceived level of addiction to cigarettes | |||||
| Very addicted | 66.3 | 47.4 | 58.5 | 47.3 | < 0.001 |
| Adjusted OR (95% CI) | 2.2 (1.5–3.2) | 1.0 (0.8–1.3) | 1.6 (1.2–2.1) | 1.00 | |
| Main effect, depressive symptoms | < 0.001 | ||||
| Main effect, cannabis use | 0.4 | ||||
| Two-way interaction test: Depressive symptoms × cannabis use | 0.2 | ||||
| Urges to smoke cigarettes in the last 24 h | |||||
| Strong/very strong/extremely strong | 48.7 | 35.5 | 48.8 | 37.4 | < 0.001 |
| Adjusted OR (95% CI) | 1.6 (1.1–2.2) | 0.9 (0.7–1.2) | 1.6 (1.2–2.1) | 1.00 | |
| Main effect, depressive symptoms | 0.002 | ||||
| Main effect, cannabis use | 0.7 | ||||
| Two-way interaction test: Depressive symptoms × cannabis use | > 0.9 | ||||
| Motivation to quit smoking | |||||
| Planning to quit | |||||
| Yes, in the next 6 months | 42.1 | 36.3 | 43.8 | 36.5 | 0.06 |
| Adjusted OR (95% CI) | 1.3 (0.9–1.7) | 1.0 (0.8–1.3) | 1.4 (1.1–1.7) | 1.00 | |
| Main effect, depressive symptoms | 0.01 | ||||
| Main effect, cannabis use | 0.8 | ||||
| Two-way interaction test: Depressive symptoms × cannabis use | 0.8 | ||||
| Made an attempt to quit smoking cigarettes in the last 24 months | |||||
| Yes | 48.1 | 36.6 | 49.1 | 40.9 | 0.002 |
| Adjusted OR (95% CI) | 1.3 (1.0–1.8) | 0.8 (0.6–1.1) | 1.4 (1.1–1.8) | 1.00 | |
| Main effect, depressive symptoms | < 0.001 | ||||
| Main effect, cannabis use | 0.2 | ||||
| Two-way interaction test: Depressive symptoms × cannabis use | 0.5 | ||||
| Made multiple attempts (≥ 2) to quit smoking cigarettes in the last 24 months | |||||
| Yes | 37.0 | 22.0 | 34.4 | 27.3 | < 0.001 |
| Adjusted OR (95% CI) | 1.6 (1.1–2.2) | 0.8 (0.6–1.0) | 1.4 (1.1–1.8) | 1.00 | |
| Main effect, depressive symptoms | < 0.001 | ||||
| Main effect, cannabis use | 0.2 | ||||
| Two-way interaction test: Depressive symptoms × cannabis use | 0.08 | ||||
| Alcohol use | < 0.001 | ||||
| High-risk alcohol use | |||||
| Yes | 35.0 | 29.3 | 20.0 | 15.3 | |
| Adjusted OR (95% CI) | 3.7 (2.4–5.6) | 2.4 (1.7–3.5) | 1.2 (0.8–1.7) | 1.00 | |
| Main effect, depressive symptoms | 0.1 | ||||
| Main effect, cannabis use | < 0.001 | ||||
| Two-way interaction test: Depressive symptoms × cannabis use | 0.5 | ||||
| Low-risk alcohol use | |||||
| Yes | 42.9 | 42.8 | 40.6 | 49.1 | |
| Adjusted OR (95% CI) | 1.3 (0.9–2.0) | 1.1 (0.8–1.5) | 0.7 (0.6–0.99) | 1.00 | |
| Main effect, depressive symptoms | 0.2 | ||||
| Main effect, cannabis use | 0.03 | ||||
| Two-way interaction test: Depressive symptoms × cannabis use | 0.05 |
Note: CI = confidence interval, OR = odds ratio.
↵* n = 2843. Data are weighted and adjusted for age, sex, education and income. Frequency of cigarette smoking was also used as a control variable in all models with the exception of daily smoking and cigarettes smoked per day. Bolded adjusted OR (95% CI) denotes significance at p < 0.05. Cigarette only: cigarette-only smokers who have never used cannabis, have not used cannabis in the last year, use cannabis occasionally (less than monthly) (reference group). p value for the main effect is the statistical difference between co-consumers with and without depressive symptoms.