Heavy Lifetime Cannabis Use and Mortality by Sex

ImportanceThe association between mortality and cannabis use remains unclear.ObjectiveTo examine sex-stratified associations of cumulative lifetime cannabis use with all-cause, cardiovascular disease (CVD), and cancer mortality in the UK Biobank population.Design, Setting, and ParticipantsThis cohort study used data from volunteers in the UK Biobank population. Participant monitoring for mortality in the UK Biobank study commenced from the point of their inclusion between 2006 and 2010 and continued until December 19, 2020. Data regarding the causes of death were sourced from the National Health Service Information Centre. Data were analyzed from inception of study inclusion to December 2020.ExposureCannabis use status was assessed by questionnaire and categorized as heavy, moderate, low, and never.Main Outcomes and MeasuresThe main outcomes were all-cause, CVD, and cancer mortality. Sex-stratified associations of cumulative lifetime cannabis use with mortality were estimated using Cox proportional hazards regression with adjustment for demographic and clinical variables.ResultsAmong 121 895 participants (54.51% females with mean [SD] age of 55.15 [7.64] years; 45.49% males with mean [SD] age of 56.46 [7.79] years) during an overall median of 11.80 years (IQR, 10.53-13.22 years) of follow-up, 2375 total deaths occurred, including 1411 deaths from CVD and 440 from cancer. In males, after full adjustment, the hazard ratios (HRs) were 1.28 (95% CI, 0.90-1.81) for all-cause mortality, 0.98 (95% CI, 0.43-2.25) for CVD mortality, and 1.09 (95% CI, 0.71-1.67) for cancer mortality among heavy cannabis users compared with never users. In females, after full adjustment, the HRs were 1.49 (95% CI, 0.92-2.40) for all-cause mortality, 2.67 (95% CI, 1.19-4.32) for CVD mortality, and 1.61 (95% CI, 0.91-2.83) for cancer mortality among heavy cannabis users compared with never users. In female current tobacco users, after full adjustment, heavy cannabis use was associated with all-cause mortality (HR, 2.25; 95% CI, 1.12-4.53), CVD mortality (HR, 2.56; 95% CI, 1.43-15.36), and cancer mortality (HR, 3.52; 95% CI, 1.50-8.33) and among never tobacco users was associated with CVD mortality (HR, 2.98; 95% CI, 1.67-6.61). In male current tobacco users, heavy cannabis use was associated with cancer mortality (HR, 2.44; 95% CI, 1.14-5.23).Conclusions and RelevanceIn this study, a positive association between CVD mortality and heavy lifetime cannabis use was observed among females. Longitudinal studies are needed in general populations to investigate the potential effects of cannabis on mortality.