Research PaperExamining the relationship between medical cannabis laws and cardiovascular deaths in the US
Introduction
The use of cannabis as therapy to treat chronic conditions or pain is now legal in a number of countries, with some nations, like Canada, providing such therapy through state-sponsored programs (Hazekamp and Heerdink, 2013, Hill, 2015).1 In the United States, there are 26 states and the District of Columbia that allowed for at least some use of cannabis as therapy be the end of 2016. Well over half of the U.S. population lives in those states.2 Other countries are currently debating whether allowing cannabis for medicinal use is appropriate. The UK recently reclassified cannabis extract as a medicine, which some think reopens serious discussion of allowing cannabis itself to be prescribed medically.3
We are interested in whether cannabis use, legal or illegal, is associated with cardiac-related mortality following the passage of state medical cannabis legalization (MCL) programs, which is the moniker for allowing cannabis for therapeutic purposes in the U.S. The association between cannabis and cardiovascular health has been documented for decades (Beaconsfield, Ginsburg, & Rainsbury, 1972; Charles, Holt, & Kirkham, 1979; Collins, Higginson, Boyle, & Webb, 1985; Fant, Heishman, Bunker, & Pickworth, 1998; Bachs and Mørland, 2001, Sidney, 2002) and is receiving renewed attention now that cannabis use is becoming even more common (Franz and Frishman, 2016, Singh et al., 2016). In population-based studies, the evidence is not conclusive (Frost, Mostofsky, Rosenbloom, Mukamal, & Mittleman, 2013; Jouanjus, Raymond, Lapeyre-Mestre, & Wolff, 2017). In one recent detailed study, Reis et al. (2017) followed a cohort of young men from young adulthood to middle age. No evidence of an association between cumulative and recent cannabis use was found.
MCL, however, might increase use among groups that would be more likely to be at risk for such an adverse cardiac event—specifically, those of advanced age. Using the National Survey on Drug Use and Health, Azofeifa (2016) documents a 333% increase in cannabis use rates among those age 65 and above and a 455% increase for those between ages 55 and 65. Conversely, overall growth in cannabis use was only 35% or about one-tenth of that for older people. There is also ample evidence that older adults are behaving in a fashion consistent with heightened medical cannabis use. Overall, new studies suggest that the Medicare enrollees are sensitive to cannabis and opioid drug policies. Bradford and Bradford (2016) show that spending on prescription drugs as part of Medicare Part D was significantly less in states that allowed for use of cannabis treat symptoms. The spending reduction was concentrated on medicines for which cannabis would be considered a viable alternative. Further suggestive evidence is provided by Nicholas and Maclean (2016) who use the Health and Retirement Study to identify that MCL increases labor supply among older adults, as well as some evidence of general health benefits, although they do not address death from cardiac events. These findings are all dependent on a heightened number of additional users of advanced age, which certainly appears to be the case. The primary drivers for such a change in use among older people over the past decade are cannabis legalization and a more general acceptance in the population of cannabis. The latter of course is a confounding factor in any study of the effects of medical cannabis. We suspect the surge has more to do with MCL, however, as Martins et al. (2016) confirms that the relative surge in use is concentrated among older individuals in MCL states.
Section snippets
Data
We use mortality data from National Vital Statistics System through the National Center for Health Statistics for 1990–2014 period to identify the number of deaths due to cardiovascular diseases in each state in each year. This dataset includes all deaths that occurred in the United States with information about socioeconomic background, including age at death, sex, the state of residence, and the cause of death for each individual. This allows us to separate deaths by age and sex as well. The
Statistical approach
We employ a standard difference-in-difference research design to assess the impact of MCL on cardiac mortality, similar to that used by Anderson, Rees, and Sabia, 2014.5 Specifically, we estimate the following regression:CVD ratest = α + β1MCLst+ Xstβ2 + δs + τt + Tt*δs +εst.
In model (1), the dependent variable is the number of cardiovascular deaths per 100,000 people in a particular sex-age group. MCLst is the policy variable,
Results
Table 2 provides descriptive statistics, first for the overall sample that includes both states passing MCL and those not. There were 303.753 cardiac-related deaths per 100,000 males per state-year over the 1990–2014 time period and 313.713 per 100,000 females. Cardiac deaths among those under 45 are comparatively rare. For the 45–64 age group, there is dramatic increase in heart deaths among both sexes, but males have approximately double the rate as females. Males and females age 65 and older
Discussion
We are the first to study whether the increased use of cannabis following its legalization for medicinal purposes is associated with cardiac health. Our study finds evidence suggesting that MCL was followed by increased cardiac mortality in states passing such laws compared with those that do not. This effect was concentrated among older individuals, particularly males, and states where there are less restrictions on dispenseries and cardholders. This effect is likely driven by increased
Conflict of interest
We received no funding for this project and therefore have nothing to declare in terms of conflict of interest.
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