Marijuana can do both, and often does both in the same session. In the first minutes after smoking or vaping, THC typically pushes blood pressure upward while also speeding the heart. Then, if you stand up, blood pressure can drop sharply enough to cause dizziness or fainting. Over the long term, the picture gets murkier: one large study tracking people for decades found that cumulative cannabis use was not significantly linked to developing high blood pressure at all. The honest answer depends on what you are asking about, whether the effect right now or the effect over years, and which compounds in the plant you are talking about.
The First Few Minutes After Using Cannabis
When someone smokes or inhales THC, the body responds with a burst of sympathetic nervous system activity. THC stimulates the “fight or flight” side of the autonomic nervous system while dialing down the parasympathetic side, the branch responsible for slowing the heart and keeping things calm.1PubMed. Cardiovascular effects of intravenous delta-9-tetrahydrocannabinol: autonomic nervous mechanisms The practical result is a quick rise in systolic blood pressure (the top number) and a noticeable increase in heart rate, sometimes adding 20 to 50 beats per minute above baseline.2PubMed Central. Role of cannabis in cardiovascular disorders
This initial spike does not last long. Within an hour or two, blood pressure tends to settle back down, and in many people it overshoots in the other direction. That overshoot is especially apparent when standing up. Researchers have a name for the dizzying drop: orthostatic hypotension. In one study, about 28 percent of participants reported severe dizziness after THC, and those who felt the worst showed the steepest drops in blood pressure and blood flow to the brain upon standing.3PubMed. Postural syncope after marijuana: a transcranial Doppler study of the hemodynamics A separate experiment found that six out of ten subjects experienced moderate to severe dizziness during standing after marijuana, with marked decreases in blood pressure and cerebral blood flow in the worst-affected group.4PubMed. Middle cerebral artery velocity during upright posture after marijuana smoking
So the short version of the acute picture is: blood pressure goes up while you are sitting or lying down, then can drop fast when you stand. Both extremes can be clinically meaningful, especially for anyone whose cardiovascular system is already under stress.
Why Cannabis Pushes Blood Pressure in Both Directions
The paradox makes more sense once you understand that THC acts on cannabinoid receptors scattered throughout the cardiovascular system. The direct effect of cannabinoids on blood vessels in the brain, for example, is vasodilation: they relax the smooth muscle in vessel walls and trigger the release of chemicals from the vessel lining that widen them further.5PubMed Central. Endocannabinoids in cerebrovascular regulation This vasodilation is part of why blood pressure can fall, and why cerebral blood flow sometimes cannot keep up with gravity when you stand.
At the same time, THC’s stimulation of the sympathetic nervous system works in the opposite direction, constricting some blood vessels and pushing the heart to beat harder and faster. The net effect at any given moment depends on which force is winning. Early on, the sympathetic jolt dominates, so pressure rises. As that wears off, the vasodilating effect takes over, and pressure sags, particularly during postural changes. Regular users develop tolerance to the sympathetic kick faster than to the vasodilation, which is why experienced users often report fewer heart-pounding sensations but may still feel lightheaded.
Does Long-Term Cannabis Use Cause High Blood Pressure?
Given that acute use raises blood pressure, you might assume that years of regular use would eventually cause chronic hypertension. The evidence, however, does not support that straightforward conclusion. The CARDIA study, a long-running project that followed young adults for decades, found that cumulative cannabis-years were not significantly associated with developing hypertension, with an adjusted hazard ratio of 0.99.6PubMed Central. Lifetime Cannabis Use and Incident Hypertension: The Coronary Artery Risk Development in Young Adults (CARDIA) Study In practical terms, the people who used cannabis for many years were no more likely to develop high blood pressure than those who did not.
That finding may seem surprising, but it aligns with the tolerance pattern. When you use cannabis regularly, the acute blood-pressure spike becomes blunted. The body adjusts to THC’s sympathetic effects within days to weeks. So while each individual session may briefly raise pressure in a new user, the cumulative cardiovascular toll, at least in terms of resting blood pressure, appears to be modest. This does not mean chronic use is risk-free, as the next section on cardiovascular events will make clear, but the specific worry that cannabis steadily ratchets up blood pressure over the years is not well supported by the largest available longitudinal data.
Cardiovascular Risks That Go Beyond Blood Pressure Numbers
Blood pressure readings do not capture the full cardiovascular story. Even though long-term cannabis use may not cause chronic hypertension, daily use is associated with a meaningfully higher risk of acute cardiovascular events. A large analysis of U.S. adults found that people who used cannabis every day had roughly 25 percent higher odds of heart attack and about 42 percent higher odds of stroke compared to nonusers.7PubMed Central. Association of Cannabis Use With Cardiovascular Outcomes Among US Adults Among people who had never smoked tobacco, the numbers were even more striking: daily cannabis use was linked to about 49 percent higher odds of heart attack and more than double the odds of stroke.7PubMed Central. Association of Cannabis Use With Cardiovascular Outcomes Among US Adults
These risks likely stem from the acute hemodynamic swings described earlier rather than from a slow buildup of pressure. The sudden spike in heart rate and blood pressure, the rapid postural drops, and the sympathetic overdrive all stress the cardiovascular system in ways that can trigger events in vulnerable people, even if resting blood pressure appears normal on a clinic reading the next morning. The association between cannabis and stroke has also been documented with synthetic cannabinoids, where case reports have described ischemic strokes in otherwise healthy young adults shortly after use.8PubMed. Synthetic cannabis and acute ischemic stroke
CBD Has a Different Effect Than THC
Cannabidiol, the non-intoxicating compound in cannabis, appears to push blood pressure in only one direction: down. In a controlled crossover study of healthy volunteers, a single dose of CBD lowered resting systolic blood pressure by about 6 mmHg and also blunted the blood pressure increase that normally occurs during stress tests.9PubMed Central. A single dose of cannabidiol reduces blood pressure in healthy volunteers in a randomized crossover study Heart rate went up slightly, but stroke volume (the amount of blood pumped per beat) went down, and overall cardiac output stayed roughly the same.
A follow-up trial tested both a single dose and seven days of repeated CBD dosing. The acute dose lowered mean arterial pressure by about 2 mmHg at rest and reduced systolic blood pressure by about 6 mmHg during stress. After a week of daily dosing, the resting effect faded, but the stress-buffering effect held, with systolic pressure during stress still about 5 to 6 mmHg lower than placebo.10PubMed Central. The effects of acute and sustained cannabidiol dosing for seven days on the haemodynamics in healthy men: A randomised controlled trial This pattern suggests that CBD’s main cardiovascular benefit may be in dampening the blood pressure spikes that accompany anxiety, physical stress, or sudden exertion, rather than in chronically lowering resting pressure.
The distinction matters because many commercial cannabis products now emphasize their CBD content. A high-CBD, low-THC strain or product would be expected to have a very different cardiovascular footprint than a high-THC product. The research so far suggests that CBD is unlikely to cause the acute blood pressure spikes or the postural drops associated with THC, and may even be mildly protective against stress-related pressure surges.
What Happens When Regular Users Stop
Here is a wrinkle many people do not anticipate: quitting cannabis after regular use can temporarily raise blood pressure. A study that monitored heavy daily users found that blood pressure increased significantly during periods of abstinence compared to periods of active use. In a subset of participants, the increases were dramatic, averaging up to about 23 mmHg systolic and 12 mmHg diastolic.11PubMed Central. Increased Blood Pressure Following Abrupt Cessation of Daily Cannabis Use
Jumps of that size are clinically significant. A 23 mmHg systolic increase could push someone from a normal range into stage 2 hypertension overnight. The effect is thought to reflect a kind of cardiovascular rebound: the body has been adapting to the chronic vasodilating effects of cannabinoids, and when those suddenly disappear, blood vessels constrict more than they would in someone who had never used. The withdrawal-related spike tends to be temporary, but for someone already on the borderline of hypertension or with heart disease, it represents a real short-term danger that rarely gets discussed.
Cannabis and Blood Pressure in Older Adults
Most cannabis research has been done in younger, generally healthy participants, so a study that specifically tracked older adults using 24-hour ambulatory blood pressure monitors is worth paying attention to. At three months of cannabis treatment, mean 24-hour systolic blood pressure dropped by about 5 mmHg and diastolic by about 4.5 mmHg, both statistically significant. The lowest point in blood pressure came about three hours after administration. The proportion of participants who had a healthy nighttime blood pressure dip (called “normal dippers”) nearly doubled, from about 27 percent before treatment to about 46 percent afterward.12PubMed. Cannabis is associated with blood pressure reduction in older adults – A 24-hours ambulatory blood pressure monitoring study
A 5 mmHg drop in systolic pressure is within the range that blood pressure medications aim for, and the improved nighttime dipping pattern is independently associated with better cardiovascular outcomes. This does not mean cannabis should be prescribed as a blood pressure drug, since the study was observational and involved a specific patient population. But it does complicate the simple narrative that cannabis raises blood pressure. In older adults, whose sympathetic nervous system responds differently to THC than a 25-year-old’s, the net effect may lean toward lowering rather than raising pressure, at least after the first few sessions.
Sex Differences in Cannabis and Blood Pressure
Animal research suggests that the cardiovascular effects of cannabis are not the same in males and females. Gonadal hormones appear to influence cannabinoid receptor density, with estrogen and testosterone modulating receptor sensitivity in different ways.13Scientific Reports. Association between cannabis use and blood pressure levels according to comorbidities and socioeconomic status This could mean that the same dose of THC produces a bigger or smaller blood pressure response depending on someone’s hormonal profile. The clinical data on this in humans is thin, but it raises an important point: generalizing from one study population to everyone can be misleading when the underlying biology is sex-dependent. If you are trying to figure out what cannabis does to your blood pressure specifically, biological sex is one of the variables that may matter.
Exercise, Cannabis, and Your Heart
A growing number of people use cannabis before workouts, so the question of how it interacts with exercise-related cardiovascular demand has become practical. A recent study had participants exercise on a stationary bike after smoking THC-predominant cannabis, vaping THC, vaping CBD, or using a control. During maximal cycling, blood pressure was similar across all conditions, meaning cannabis did not amplify the normal exercise-related blood pressure rise. However, after exercise, people who had smoked THC showed elevated pulse pressure (the gap between systolic and diastolic readings), jumping from about 43 mmHg before the session to about 50 mmHg afterward, compared with no change in the control group.14American Physiological Society (AJP – Heart and Circulatory Physiology). The acute cardiovascular response to dynamic exercise and recovery following cannabis use
Wider pulse pressure after exercise suggests the heart is working harder during recovery or that vascular stiffness has temporarily increased. The vaping-THC and vaping-CBD groups showed smaller changes, suggesting that the combustion products in smoke may contribute to the effect. This is a single study and the numbers are modest, but for anyone who regularly combines cannabis with physical activity, the post-exercise recovery period may carry a slightly different hemodynamic profile than they would expect.
Synthetic Cannabinoids Are a Different Beast
Products marketed as “synthetic cannabis” or “spice” are chemically distinct from plant-derived THC and tend to produce more aggressive cardiovascular effects. In animal studies, several synthetic cannabinoid compounds caused dose-dependent increases in blood pressure that were significantly higher than what THC produced at comparable doses.15PubMed Central. Synthetic cannabinoids found in “spice” products alter body temperature and cardiovascular parameters in conscious male rats While THC showed a trend toward raising blood pressure in the same experiments, the synthetic compounds were more potent and more consistent in their hypertensive effects.
Case reports of ischemic stroke in young adults using synthetic cannabinoids reinforce this concern.8PubMed. Synthetic cannabis and acute ischemic stroke The clinical profiles in these cases tend to be more severe than what is seen with plant cannabis, likely because synthetic compounds bind cannabinoid receptors more tightly and for longer durations. Anyone using synthetic cannabinoid products faces a blood pressure and cardiovascular risk profile that is substantially worse than what the plant-based research would predict.
Terpenes and the Rest of the Plant
Cannabis contains dozens of terpenes, the aromatic compounds responsible for the plant’s distinctive smell, and some of these molecules have their own effects on blood vessels. A review of the literature on monoterpenes and monoterpenoids (the class most abundant in cannabis) found that many of these compounds have hypotensive and bradycardic effects, meaning they lower blood pressure and slow the heart. Their mechanism appears to involve blocking calcium channels in vascular smooth muscle, which prevents the contraction that narrows blood vessels.16IntechOpen. Effects of Terpenes and Terpenoids of Natural Occurrence in Essential Oils on Vascular Smooth Muscle and on Systemic Blood Pressure: Pharmacological Studies and Perspective of Therapeutic Use
This adds another layer to the “does cannabis raise or lower blood pressure” question. The THC in a given product may push pressure up, the CBD may push it down, and the terpene profile may contribute a further vasodilating influence. Whole-plant cannabis is not a single drug; it is a cocktail. Two strains with the same THC percentage but different terpene profiles could, in theory, have meaningfully different cardiovascular effects. This kind of complexity is why research that tests isolated THC in a lab tells only part of the story, and why individual experiences with blood pressure after cannabis use vary so widely.
Practical Guidance for People Who Monitor Their Blood Pressure
If you take blood pressure readings at home, the timing relative to cannabis use matters enormously. A reading taken 15 minutes after smoking might be artificially high, while one taken two hours later, especially while standing, might be artificially low. Neither captures your true resting baseline. The most representative reading comes at least several hours after your last use, seated and at rest.
For people on blood pressure medications, the postural hypotension effect is worth watching carefully. Many antihypertensive drugs already lower standing blood pressure, and adding cannabis to the mix could amplify the drop. This is especially relevant for older adults on multiple medications, the group where the 24-hour monitoring study showed cannabis lowering pressure even further. Whether that additional drop is a benefit or a risk depends on where the person’s blood pressure started.
People who use cannabis daily and are considering quitting should be aware of the rebound hypertension that can occur during the first days of abstinence. A gradual taper may be gentler on the cardiovascular system than abrupt cessation, though research specifically testing that approach is limited. Anyone with existing heart disease or a history of stroke should treat both the acute effects of cannabis use and the withdrawal period as times of heightened cardiovascular vulnerability.