Heavy cannabis use was associated with a more than twofold increase in risk for lung cancer over 40 years.
Summary
n=49.321 Swedish men (age 18–20 y.), 40-year follow-up; heavy cannabis use (>50 times lifetime, n=831) was significantly associated with more than double the risk of lung cancer (HR=2,12; 95% CI 1,08–4,14), even after adjustment for tobacco use, alcohol, respiratory diseases and socioeconomic status.
P
PopulationMale Swedish military recruits, n=44.284 (evaluated), age 18–20 years at enrollment 1969–1970
I
InterventionHeavy cannabis use (>50 times use in history) recorded at enrollment
C
ControlNo or lighter cannabis use
O
OutcomeHazard ratio for lung carcinoma with heavy cannabis use: HR 2,12 (95 % CI 1,08–4,14), adjusted for tobacco, alcohol, respiratory diseases and socioeconomic status
Confidence in the evidence
Very lowLowModerateHigh
Low
The second of four GRADE levels, the effect estimate is of limited reliability.
<h4>Purpose</h4>Cannabis (Cannabis) smoke and tobacco smoke contain many of the same potent carcinogens, but a critical-yet unresolved-medical and public-health issue is whether cannabis smoking might facilitate the development of lung cancer. The current study aimed to assess the risk of lung cancer among young Cannabis users.<h4>Methods</h4>A population-based cohort study examined men (n = 49,321) aged 18-20 years old assessed for cannabis use and other relevant variables during military conscription in Sweden in 1969-1970. Participants were tracked until 2009 for incident lung cancer outcomes in nationwide linked medical registries. Cox regression modeling assessed relationships between cannabis smoking, measured at conscription, and the hazard of subsequently receiving a lung cancer diagnosis.<h4>Results</h4>At the baseline conscription assessment, 10.5 % (n = 5,156) reported lifetime use of Cannabis and 1.7 % (n = 831) indicated lifetime use of more than 50 times, designated as "heavy" use. Cox regression analyses (n = 44,284) found that such "heavy" cannabis smoking was significantly associated with more than a twofold risk (hazard ratio 2.12, 95 % CI 1.08-4.14) of developing lung cancer over the 40-year follow-up period, even after statistical adjustment for baseline tobacco use, alcohol use, respiratory conditions, and socioeconomic status.<h4>Conclusion</h4>Our primary finding provides initial longitudinal evidence that cannabis use might elevate the risk of lung cancer. In light of the widespread use of Cannabis, especially among adolescents and young adults, our study provides important data for informing the risk-benefit calculus of Cannabis smoking in medical, public-health, and drug-policy settings.</h4>