Marijuana users three times more likely to die from high blood pressure

Marijuana use may increase people's risk of death from hypertension (high blood pressure), a new study has found. The findings confirm previous associations that suggested recreational marijuana use may have potentially debilitating cardiovascular effects.

Cardiovascular diseases constitute the leading cause of death worldwide, despite most of them being preventable. More than 17 million people died of these diseases in 2015 globally.

In recent years, studies have linked marijuana use to cardiovascular problems. As a growing number of countries move to decriminalise marijuana, understanding whether its use increases cardiovascular mortality is beginning to look like a public health priority.

"Steps are being taken towards legalisation and decriminalisation of marijuana in the US, and rates of recreational marijuana use may increase substantially as a result," lead author Barbara Yankey, from Georgia State University said in a statement. "However, there is little research on the impact of marijuana use on cardiovascular and cerebrovascular mortality."

The study now published in the European Journal of Preventive Cardiology looks at the marijuana consumption of US adults and whether there is a link between their use of the drug and cardiovascular mortality.

Looking for marijuana users

Obtaining data about people's marijuana consumption is challenging, as there is no longitudinal data available on marijuana use. To get around this problem, the researchers designed a retrospective follow-up study of the 2005-2006 National Health and Nutrition Examination Survey, in which participants aged 20 years and above had been asked if they had ever used marijuana. Those who answered "yes" were considered marijuana users by the researchers in this present study.

To get an approximation of how long the participants had been consuming marijuana, the scientists looked at the age people had when they first tried marijuana and subtracted this from their current age.

The team also looked at mortality data in 2011 from the National Centre for Health Statistics. Combining both datasets, the researchers estimated the associations of marijuana use, and duration of use, with death from hypertension, heart disease, and cerebrovascular disease. They controlled for other risk factors cigarette use and demographic variables such as sex, age, and ethnicity.

A total of 1,213 participants were considered for the analyses. 34% of them used neither marijuana nor cigarettes, 21% used only marijuana, 20% used marijuana and smoked cigarettes, 16% used marijuana and were past-smokers, 5% were past-smokers and 4% only smoked cigarettes. According to the scientists' calculations, the average duration of marijuana use was 11.5 years.

The analyses of the data revealed that compared to non-users, marijuana users had a 3.42 times higher risk of death from hypertension and a 1.04 times greater risk for each year of use. There was however no association between marijuana use and death from heart disease or cerebrovascular disease.

There are obvious limitations to the study, especially the way marijuana use was calculated - it is not certain that participants used the drug continuously since they first tried it. Due to the way marijuana use was estimated, more than half of the participants were considered marijuana users, which seems unlikely.

This is nevertheless a first helpful step to assess the long-term health risks posed by marijuana. The question of what it does to the heart needs to be addressed as more and more people around the world use it.

"Given an increasing trend to decriminalise use of marijuana, it is important to understand the health risks of its use. This study attempted to work out the risk of various heart diseases from smoking marijuana, but its findings are far from definite. Since marijuana use is illegal in many jurisdictions, it is very hard to be certain about the health risks it poses, " explained Tim Chico, a reader in cardiovascular medicine at the University of Sheffield, who was not involved with the study.

"However, although this paper has limitations there is enough evidence from other research to strongly suspect marijuana use increases the risk of some forms of heart disease, and it is certainly not harmless."