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One in three adults in the U.S. has high blood pressure, a condition known as hypertension. Left unmanaged, it can lead to cardiovascular disease, which is characterised by an increased risk of stroke, heart attack, and even heart failure. A number of factors, including poor diet, stress, physical inactivity, alcohol, and tobacco use increase the risk of developing hypertension.
Some of the effects of cannabis on blood pressure, particularly the acute effects, are well understood and documented. However, research studies describing other effects, especially long-term adverse or positive effects, are limited, and often plagued by poor study design or the fact that findings from animal studies don’t always neatly transfer to human subjects.
Further, many research findings are highly generalized, focusing on THC while neglecting consideration of the numerous other cannabinoids. Logically, a cannabis strain high in the psychoactive cannabinoid THC would yield different results from a strain high in the largely non-psychoactive cannabinoid CBD.
Perhaps most frustrating, published studies investigating differences between consumption methods – such as the effects of smoking cannabis versus ingested edibles – are essentially nonexistent.
With these limitations in mind, here is what we do know.
Does cannabis raise blood pressure? Studies suggest shortly after consumption, occasional users will experience a mild to moderate dose-dependent increase in blood pressure and heart rate, followed by a modest hypotensive effect (a decrease in blood pressure). The onset of peak effects like elevated heart rate and blood pressure occur within 10 to 15 minutes after consumption.
Users can develop a tolerance to the initial effects over a period of a few days to weeks, and repeated use has been associated with lowered heart rate and blood pressure immediately following consumption. Anecdotally, many people report that cannabis helps them maintain healthy blood pressure levels, an effect supported by research studies.
Here’s an interesting piece of “non-trivial trivia” you can use to impress friends at your next cannabis-inspired intellectual discussion: posture during consumption may influence blood pressure. Suppose you’re sitting or lying on your couch – your blood pressure will temporarily increase immediately following consumption. Once you stand up, blood pressure will drop. In fact, if you stand up suddenly, blood pressure could drop significantly enough to induce enough lightheadedness to make you feel like you’re about to faint (don’t worry, it’s unlikely you’d actually pass out).
On the other hand, if you’re standing up when you imbibe, blood pressure may decrease without ever initially increasing. However, there isn’t a lot of published data verifying this effect. (If you’ve done your own comparative measurements, feel free to share in the comments section below!)
As far as serious adverse risks, a UC San Francisco longitudinal Coronary Artery Risk Development in Young Adults (CARDIA) study analysing data from 3,617 African American and Caucasian adults over a 15 year period found there was no long-term causal link between cannabis consumption and the risk of heart attack or stroke.
However, there are a limited number of animal studies and human case reports that suggest a link between acute intoxication and stroke or heart attack. But, these findings have been called into question by a 2006 report published in the Forensic Science, Medicine and Pathology Journal: “Despite the drug’s extreme popularity, reports of cannabis-related stroke and myocardial infarction are so rare as to still be reportable.”
Further, human case reports often don’t take into account that in these rare events, people may have consumed cannabis in conjunction with alcohol, tobacco, or stimulants contemporaneously or shortly before the incident.
Nonetheless, a Harvard Medical School study concluded that for an hour after consuming cannabis (especially in at-risk populations; e.g. seniors), the odds of suffering a heart attack increases by five times. Risk returns to normal within two hours. Notably, sex carries a comparable risk increase. This begs the question: does combining cannabis and sex exponentially increase one’s chances of a heart attack? We’re eagerly awaiting a follow-up study from Harvard to answer this question.
It’s long been established that the body’s endocannabinoid system (whose naturally occurring chemicals behave similarly to cannabinoids found in cannabis) play an important role in regulating many of the body’s key physiological functions, including cardiovascular function.
A growing body of research shows that anandamide – the body’s naturally occurring version of THC – relaxes blood vessels, the implication being that by allowing blood to flow more freely, anandamide helps lower blood pressure.
Notably, the National Institute on Alcohol Abuse & Alcoholism published a report concluding “endocannabinoids tonically suppress cardiac contractility in hypertension,” and that “targeting the endocannabinoid system offers novel therapeutic strategies in the treatment of hypertension.”
The degree to which the endocannabinoid system plays a role in regulating blood pressure has long inspired researchers to examine if we could treat hypertension by manipulating the endocannabinoid system.
However, we’re not there yet. Remarkably, despite the fact that cannabinoids have been studied for their potential as antihypertensive agents since the 1970s, no cannabinoid-based medications have been officially approved to treat hypertension. Moreover, despite an ever-growing body of anecdotal evidence and numerous studies suggesting the regular use of cannabis does appear to produce long-term lower blood pressure levels, we lack the sort of rigorous human studies that would allow physicians to confidently say, “Use cannabis to treat your hypertension!”
As we continue to develop a better understanding of the cannabinoid receptor system’s role in cardiovascular regulation, we’ll soon be able to more confidently identify the therapeutic role for cannabinoids in blood pressure control.