Frequent cannabis use increases the risk of cardiovascular disease in women

In a recent study published in JAMA Network Open, researchers examined whether cannabis use is associated with mortality from all causes, cancer, and cardiovascular disease (CVD).

Their results showed that heavy cannabis use was associated with a significantly higher risk of CVD mortality among women. However, they found no association between cannabis use and cancer and all-cause mortality among the entire sample of men and women.

Cannabis is the most commonly used illegal drug in the world, and its increasing legalization underscores the need to understand its impact on health.

Previous studies have suggested possible cardiovascular risks associated with cannabis use, but these studies were often limited to specific populations, reducing the general applicability of their findings.

In addition, there was a lack of studies examining the differential effects of cannabis on men and women. Although the use of cannabis for medical purposes is increasing, its safety and effectiveness for various conditions remain unclear.

Some studies have suggested a link between heavy cannabis use and increased mortality from all causes and cardiovascular disease. However, other studies have not found such a link, often due to methodological limitations such as small sample sizes, short follow-up periods, or limited age range of participants.

This study examined the associations between lifetime cannabis use and mortality from CVD, cancer and all causes in a large general population sample, controlling for sex.

The study used data from the UK Biobank, a large biomedical database of 502,478 people aged 40 to 69 years recruited from 2006 to 2010 from 22 UK cities.

Participants provided detailed information about their health through questionnaires, interviews, physical examinations and biological samples, and their data were linked to mortality records through December 19, 2020.

Cannabis use was self-reported and categorized as never, low, moderate, and heavy.

The study analyzed data from 121,895 UK Biobank participants, with an average age of 55.15 years for women and 56.46 years for men.

Among the participants, 3.88% of men and 1.94% of women were heavy cannabis users. Over a median follow-up period of 11.8 years, there were 2375 deaths, including 440 from cancer and 1411 from CVD.

Heavy cannabis use among men was associated with an increased risk of all-cause mortality (hazard ratio (HR) 1.28), but was not significantly associated with mortality from CVD or cancer after controlling for all factors.

In women, heavy cannabis use was associated with a higher risk of CVD mortality (RR 2.67) and a nonsignificant increase in all-cause and cancer mortality after full adjustment.

Particularly among female smokers, heavy cannabis use significantly increased the risks of all-cause mortality (RR 2.25), CVD (RR 2.56), and cancer (RR 3.52).

In male smokers, the risk was increased only for cancer mortality (RR 2.44). Excluding participants with comorbidities did not show significant associations between heavy cannabis use and mortality.

This study diverges from previous studies that have primarily examined all-cause mortality in younger populations, showing an increased risk associated with cannabis use.

Few studies have examined the association between cannabis use and CVD mortality, with varying results. Some studies indicated a significant association, while others found none.

Strengths of the study include the large sample size and standardized data collection protocols from the UK Biobank. However, cross-sectional design limits the ability to establish causality, and low response rates may introduce participant bias.

The study's focus on middle-aged UK participants limits its applicability to other demographic groups.

Future research should include longitudinal studies to examine the possible causal effect of cannabis use on mortality, with an emphasis on precise measures of cannabis use, including frequency, dosage, and methods of consumption.

These studies should also seek to understand sex differences in cannabis exposure and the association between cannabis use and cancer mortality, given the current mixed evidence.