In total, 79 cases of lung cancer and 324 controls were included in the study. The risk of lung
cancer increased 8% (95% confidence interval (CI) 2–15) for each joint-yr of cannabis smoking,
after adjustment for confounding variables including cigarette smoking, and 7% (95% CI 5–9) for
each pack-yr of cigarette smoking, after adjustment for confounding variables including cannabis
smoking. The highest tertile of cannabis use was associated with an increased risk of lung cancer
(relative risk 5.7 (95% CI 1.5–21.6)), after adjustment for confounding variables including cigarette
smoking.