In a recent study published in JAMA Network Open, researchers explored whether cannabis use is linked to mortality from all causes, cancer and cardiovascular disease (CVD).
Their findings indicate that heavy cannabis use is associated with a significantly higher risk of CVD mortality among females. However, they observed no association between cancer and all-cause mortality among the entire sample of males and females.
Study: Heavy Lifetime Cannabis Use and Mortality by Sex. Image Credit: Rawpixel.com/Shutterstock.com
Background
Cannabis is the most commonly used illegal drug worldwide, and its increasing legalization underscores the need to understand its health impacts.
Previous research has suggested potential cardiovascular risks associated with cannabis use, but these studies often focused on specific populations, limiting the generalizability of their findings.
Furthermore, there has been a lack of research examining the differential effects of cannabis on males and females. Although cannabis use for medical purposes is expanding, its safety and efficacy for various conditions remain unclear.
Some studies have suggested a link between heavy cannabis use and increased all-cause and cardiovascular mortality. Still, others have found no such associations, often constrained by methodological limitations like small sample sizes, short follow-up periods, or limited age ranges of participants.
Only one prior study explored the relationship between cannabis use and cancer mortality, finding no significant link.
About the study
This study addressed existing gaps by examining sex-stratified links of lifetime cannabis use to CVD, cancer, and all-cause mortality in a large general population sample.
The cohort study utilized data from the UK Biobank, a large-scale biomedical database comprising 502,478 individuals aged 40 to 69, recruited from 2006 to 2010 from 22 cities across the UK.
Participants provided detailed health information through questionnaires, interviews, physical assessments, and biological samples, and their data was linked to mortality records up to December 19, 2020.
Cannabis use was self-reported and categorized into never, low, moderate, and heavy use based on lifetime frequency.
The study assessed the association between cannabis use and mortality using Cox proportional hazards regression models, adjusting for clinical and demographic variables.
Analyses were stratified by sex to address potential differences between males and females. Mortality outcomes were defined using codes from the International Statistical Classification of Diseases and Related Health Problems, 10th Revision, and various covariates such as age, education, income, smoking history, alcohol use, hypertension, diabetes, dyslipidemia, body mass index (BMI), prior CVDs, and antidepressant use were included in the models.
The study employed Kaplan-Meier survival analyses, considering two-sided P values less than 0.05 as significant.
Findings
The study analyzed 121,895 UK Biobank participants, aged 55.15 years on average for females and 56.46 years for males.
Among the participants, 3.88% of males and 1.94% of females were heavy cannabis users. Over a median follow-up of 11.8 years, there were 2,375 deaths, including 440 due to cancer and 1,411 due to CVD.
Heavy cannabis use in males was associated with an increased risk of all-cause mortality, with a hazard ratio (HR) of 1.28, but not significantly with CVD or cancer mortality after adjusting for all factors.
In females, heavy use of cannabis was associated with a higher risk of mortality from CVD (HR 2.67) and a non-significant increase in all-cause and cancer mortality after full adjustment.
Notably, among female tobacco users, heavy cannabis use significantly increased risks for all-cause mortality (HR 2.25), CVD mortality (HR 2.56), and cancer mortality (HR 3.52).
In contrast, male tobacco users saw an increased risk only for cancer mortality (HR 2.44). Excluding participants with comorbidities showed no significant associations between heavy use of cannabis and mortality.
The findings suggest a sex-specific impact of heavy cannabis use on mortality, particularly in females.
Conclusions
This study diverges from previous research that largely examined all-cause mortality among younger populations, showing a heightened risk associated with cannabis use.
Few studies addressed the link between cannabis use and CVD mortality, with mixed findings. Some studies indicated a significant association, while others did not.
The study’s strengths include a large sample size and standardized data collection protocols from the UK Biobank. However, the cross-sectional design limits causal inference, and the low response rate might introduce participant bias.
The study’s focus on middle-aged UK participants limits generalizability to other demographics.
Self-reported data on cannabis use and lack of recent usage patterns, dosage information, and follow-up on cannabis use during the study period are significant limitations.
Future research should involve longitudinal studies to explore the possible causal impact of cannabis use on mortality, with a focus on precise measurements of cannabis use, including frequency, dosage, and methods of consumption.
These studies should also aim to understand the sex-specific impacts and the links between of cannabis use and cancer mortality, given the ambiguous current evidence.