Regular cannabis use was linked to greater cardiovascular risks, especially in people who did not also smoke tobacco | Research

The takeaway

In an analysis of electronic health records, regular cannabis use was associated with higher rates of stroke, arrhythmia, and death, with the strongest associations found in cannabis users who did not also use tobacco.

Cardiologists, primary care providers counseling cannabis users, and public health researchers assessing cannabis cardiovascular safety.

Cannabis cardiovascular risks strongest in non-tobacco users

What the researchers found

In the total sample and non-tobacco subgroup, regular cannabis use was significantly associated with greater risk for stroke (CVA), arrhythmia, subarachnoid hemorrhage (SAH), and all-cause mortality. Among tobacco users, cannabis was only associated with greater risk for arrhythmia and SAH. Tobacco users had the highest overall cardiovascular disease prevalence regardless of cannabis status.

Why it matters

The finding that cannabis cardiovascular risks are more apparent in non-tobacco users suggests cannabis is an independent cardiovascular risk factor whose effects may be masked in tobacco users by their already-elevated baseline risk.

The numbers in context

8,944 cannabis users matched to controls. 4,682 with tobacco use disorder, 4,262 without. Non-tobacco cannabis users: significant associations with CVA, arrhythmia, SAH, and mortality. Tobacco-using cannabis users: significant for arrhythmia and SAH only.

How the study worked

Retrospective analysis of electronic health records via IBM Watson Health Explorys. 8,944 cannabis-using patients matched to controls using propensity scores on demographics, zip code income, BMI, and tobacco status. Subgroup analyses for tobacco users (n=4,682) and non-tobacco users (n=4,262).

What this study cannot tell us

Retrospective EHR data from a single health system (Cleveland). Cannabis use identified by diagnosis codes and drug screens, which may undercount casual users. Cannot establish causation. Unmeasured confounders possible despite matching.

How to read the evidence

Large matched-cohort EHR study with propensity scoring, but retrospective design and potential unmeasured confounders.

When this study was published

2020 study. Important early evidence on cannabis-specific cardiovascular risk independent of tobacco.

The bigger picture

As cannabis use increases and tobacco use declines, the cardiovascular effects of cannabis may become more clinically visible. This study suggests that cannabis-only users may need cardiovascular screening that has traditionally been reserved for tobacco smokers.

Questions still open

What mechanisms drive cannabis-associated cardiovascular risk? Does the route of cannabis administration (smoking vs. edibles) affect cardiovascular outcomes? Would prospective studies with controlled exposure confirm these associations?

Common questions

Why were risks higher in non-tobacco users?

Tobacco users already have very high cardiovascular disease rates, so the additional risk from cannabis may be harder to detect statistically. In non-tobacco users, the cannabis-associated risk stood out more clearly against a lower baseline.

Does this mean cannabis causes heart problems?

This observational study found associations but cannot prove causation. However, the associations persisted after matching on multiple factors, suggesting cannabis may be an independent cardiovascular risk factor.

Read the original research

The association between regular cannabis use, with and without tobacco co-use, and adverse cardiovascular outcomes: cannabis may have a greater impact in non-tobacco smokers.

The American journal of drug and alcohol abuse, 46(4), 454-461

View on PubMed ↗Publisher’s paper ↗

Citation

Winhusen, Theresa; Theobald, Jeff; Kaelber, David C; Lewis, Daniel. (2020). The association between regular cannabis use, with and without tobacco co-use, and adverse cardiovascular outcomes: cannabis may have a greater impact in non-tobacco smokers.. The American journal of drug and alcohol abuse, 46(4), 454-461. https://doi.org/10.1080/00952990.2019.1676433