The research investigating the relationship between marijuana use and blood pressure is complex and often produces conflicting results.
The best conclusion that can be made at this point is that there is a mild increase in blood pressure when someone smokes marijuana, but over time, blood pressure may decrease.
According to the American Heart Association (AHA), when your heart pumps blood through your arteries, the blood moving through the arteries produces a force against the artery wall.
The force of the blood pressing against the walls of the arteries is measured as systolic blood pressure. The force of the blood pressure against the artery walls in between heartbeats (when the heart is at rest) is measured as diastolic blood pressure.
Normal blood pressure is a measurement of less than 120/80 mmHg (systolic/diastolic).
The AHA reports that high blood pressure (hypertension) occurs when the blood pressure in your arteries is elevated consistently.
Research findings suggest that high systolic blood pressure is of particular concern and more likely to be associated with cardiovascular issues like an increased risk for stroke or heart disease.
A diagnosis of hypertension means the heart must work harder to pump blood. This weakens your heart, and over time, it causes strain that leaves you more susceptible to heart disease. Due to the pressure on the arterial walls, your arteries can get damaged.
It is estimated that hypertension affects about a third of Americans, but it does not typically result in serious symptoms for quite some time. If left untreated, it leads to a greater risk for heart disease and other cardiovascular issues.
There are many different conditions (risk factors) that can increase the probability of developing high blood pressure, such as a lack of exercise, being overweight, smoking, drinking alcohol, and using drugs to excess.
The body of research investigating the use of cannabis products and its relationship to developing hypertension has produced mixed results.
Several large studies have been cited frequently, but all the studies have some methodological flaws. This indicates that more research needs to be performed before the exact relationship between the use of marijuana and hypertension can be determined.
A large study published in the European Journal of Preventive Cardiology in 2017 is one of the most cited studies regarding the relationship between marijuana use and hypertension. The study looked at participants ages 20 and older who responded to questions on the United States National Health and Nutrition Examination Survey.
Using a statistical technique known as multiple regression, those using marijuana were compared to those not using marijuana on rates of hypertension, other heart disease, and death due to cerebrovascular problems (stroke).
The findings indicated that marijuana users were more likely than non-marijuana users to die because of factors related to hypertension. The length of time the person used marijuana was also related to this increased risk, with individuals using marijuana for greater lengths of time being more likely to have death related to hypertension or factors associated with vascular disease.
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This relationship remained when other factors associated with hypertension, such as cigarette smoking and dietary factors, were controlled for.
However, the researchers warned that their findings are only preliminary and more research needs to be done.
The researchers did not physically measure the levels of cannabinoids (the psychoactive factors in cannabis) in the systems of the participants to determine their extent of marijuana use. They instead relied on the self-report of participants to determine how much marijuana was used. Using self-reported data is often an unreliable measure in research studies, especially when the variable can be measured physically.
An earlier large study published in the Journal of Hypertension in 2016 looked at data on blood pressure taken at four different points during a physical examination and cannabis use. Again, the statistical technique of multiple regression was used to examine the relationship between the use of cannabis and blood pressure.
It was found that the active cannabis use was associated with an initial increase in systolic blood pressure, but there was no association with the use of cannabis and an increase in diastolic blood pressure or with long-term issues associated with hypertension.
The researchers commented that their findings are only preliminary. Marijuana use was determined by self-reports, like most other studies of this type. Actual laboratory measurements of THC levels in the blood and its relationship to hypertension should be conducted in the future for a better picture of how cannabis use affects blood pressure.
Because many states have recently legalized the medicinal or recreational use of marijuana products, there is ongoing research to determine how cannabis use affects numerous health issues.
The current body of research suggests there might be an increase in blood pressure associated with recent cannabis use, but the findings cannot be inferred to determine whether there is a causal relationship, such that use of marijuana causes high blood pressure or death related to cardiovascular disease.
The way marijuana is taken may also affect blood pressure, such that eating marijuana may not affect blood pressure to the extent that smoking it does. Little research exists at this time to investigate this situation.
Research studies are not always consistent in their findings. Current studies cannot determine whether or not acute increases in blood pressure associated with cannabis use are linked with chronic elevations in blood pressure.
The major body of research focuses on the effects of THC (tetrahydrocannabinol), the ingredient in cannabis that produces the high or psychoactive effects. There are more than 100 other substances found in cannabis, including cannabidiol (CBD), which is the common substance from cannabis that is used medicinally.
Some research suggests that CBD use may actually lower blood pressure in people who had not used cannabis products previously. Again, more research needs to be conducted.
Many people who read research studies that set out to investigate the relationship between marijuana use, high blood pressure, and potential heart disease might become confused by the conflicting findings. This is because the research is still in its infancy. Ongoing research is attempting to tease out the actual associations between cannabis and hypertension.
(November 2017) Understanding Blood Pressure Readings. American Heart Association. Retrieved March 2019 from https://www.heart.org/en/health-topics/high-blood-pressure/understanding-blood-pressure-readings
(November 2017) A study using the National Health and Nutrition Examination Survey linked mortality file. European Journal of Preventive Cardiology. Retrieved March 2019 from https://www.ncbi.nlm.nih.gov/pubmed/28789567
(August 2016) Cannabis Use and Blood Pressure Levels: United States National Health and Nutrition Examination Survey, 2005–2012. Journal of Hypertension. Retrieved March 2019 from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5237375/
(June 2017) A single dose of cannabidiol reduces blood pressure in healthy volunteers in a randomized crossover study. JCI Insight. Retrieved March 2019 from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5470879/