Does cannabis reduce hypertension?

With the increasing prevalence of hypertension at a time when states are liberalising cannabis laws, people want to know: what are the effects of cannabis on blood pressure? Does cannabis reduce hypertension? The answers depend largely on who you ask or what study you read. In the United States, one in three adults has high blood pressure. If left untreated, it can lead to cardiovascular disease, with an increased risk of stroke, heart attack and even heart failure. A number of factors, including poor diet, stress, physical inactivity, alcohol consumption and smoking, increase the risk of hypertension.

Some of the effects of cannabis on blood pressure, particularly the acute effects, are well understood and documented. However, studies describing other effects, especially positive or negative long-term effects, are limited and often hampered by poor study design or by the fact that the results of animal studies are not always fully transferable to human subjects. Perhaps most frustratingly, published studies on the differences between methods of consumption – such as the effects of smoked versus ingested cannabis – are virtually non-existent.

Short and long term effects of cannabis use

Does cannabis raise or reduce hypertension? Studies suggest that shortly after use, occasional users will experience a dose-dependent mild to moderate increase in blood pressure and heart rate, followed by a modest hypotensive effect (a decrease in blood pressure). Peak effects, such as increased heart rate and blood pressure, occur within 10 to 15 minutes of consumption.

Users may develop tolerance to the initial effects over a period of days to weeks, and repeated use has been associated with a decrease in heart rate and blood pressure immediately after use. Anecdotally, many people report that cannabis helps them maintain healthy blood pressure, an effect confirmed by research studies.

Cannabis and stroke or heart attack

With regard to serious risks, a longitudinal study from UC San Francisco entitled Coronary Artery Risk Development in Young Adults (CARDIA), analysing data from 3,617 African-American and Caucasian adults over a 15-year period, showed that there was no long-term causal link between cannabis use and the risk of heart attack or stroke. However, a limited number of animal studies and human case reports suggest a link between acute intoxication and stroke or myocardial infarction. But these findings were challenged by a 2006 report in the Forensic Science, Medicine and Pathology Journal: “Despite the extreme popularity of the drug, cases of cannabis-related stroke and myocardial infarction are so rare that they remain unreported.

Moreover, human case reports often fail to take into account that in these rare cases, people may have used cannabis together with alcohol, tobacco or stimulants, either simultaneously or shortly before the incident. Nevertheless, a Harvard Medical School study concluded that within one hour of marijuana use (particularly in at-risk populations such as the elderly), the likelihood of having a heart attack increases fivefold. The risk returns to normal within two hours. It should be noted that sexual intercourse leads to a comparable increase in risk.

Does endocannabinoid system has the ability to reduce hypertension?

It has long been established that the body’s endocannabinoid system (whose natural chemicals behave in a similar way to the cannabinoids found in cannabis) plays an important role in regulating many key physiological functions in the body, including cardiovascular function.

A growing body of research shows that anandamide – the body’s natural version of THC – relaxes blood vessels, meaning that by allowing blood to flow more freely, anandamide helps lower blood pressure.

In particular, the National Institute on Alcohol Abuse & Alcoholism published a report concluding that endocannabinoids tonically suppress cardiac contractility in hypertension and that targeting the endocannabinoid system offers new therapeutic strategies in the treatment of hypertension. The extent to which the endocannabinoid system plays a role in regulating blood pressure has long prompted researchers to examine whether hypertension can be treated by manipulating the endocannabinoid system.

However, we are not there yet. Remarkably, although cannabinoids have been studied for their potential as antihypertensive agents since the 1970s, no cannabinoid-based drugs have been officially approved for the treatment of hypertension. Furthermore, despite a growing body of anecdotal evidence and numerous studies suggesting that regular cannabis use does indeed appear to result in long-term reductions in blood pressure, we lack the kind of rigorous human studies that would allow physicians to say with confidence, Use cannabis to treat your hypertension!

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