Smoking cigarettes poses several health risks, from heart disease to cancer, but the effects of marijuana are still inconclusive. The drug is believed to hold medical promise in several areas, like treating nausea in cancer patients, but researchers believe it may do more harm than good. A recent study published in European Journal of Preventive Cardiology found smoking pot can raise a smoker's risk from dying of high blood pressure.

Those who reported marijuana use were more than three times as likely to die from high blood pressure than non-smokers. Moreover, for each year of marijuana use, smokers' risk grew by four percent. The average duration for using marijuana, a Schedule I drug, or believed to have a high potential for abuse, was 12 years.

“This is not surprising since marijuana is known to have a number of effects on the cardiovascular system. Marijuana stimulates the sympathetic nervous system, leading to increases in heart rate, blood pressure, and oxygen demand,” said Barbara A. Yankey, study lead author and a PhD student in the School of Public Health at Georgia State University, in a statement.

Read More: 7 Hidden Health Dangers Of Smoking Marijuana

The Brain On THC

Researchers believe tetrahydrocannabinol (THC) — the active ingredient in marijuana — is linked to some heart health risks. THC's chemical structure is similar to the brain chemical anandamide, which allows the body to recognize THC, causing it to alter normal brain communication. Anandamide functions as a neurotransmitter by sending out chemical messages between neurons through the nervous system, which influence pleasure, memory, thinking, concentration, and sensory and time perception.

This gives THC the ability to attach to cannabinoid receptors on neurons in these brain areas and activate them. The endocannabinoid system uses these cannabinoid neurotransmitters for nervous system functioning, including heart rate function. The presence of THC can lead to an increase in heart rate and blood pressure. A rise in blood pressure means the heart has to use more force to circulate blood throughout the body; this can damage blood vessels, and potentially lead to a buildup of plaque, raising the risk of heart complications like a heart attack.

THC On Heart Health

Researchers at Georgia State University sought to determine if long-term marijuana use is associated with an increased risk of high blood pressure. Data was pulled from over 1,200 participants who completed responses to the 2005-2006 National Health and Nutrition Examination Survey (NHANES) — an annual federal survey conducted to evaluate Americans' diets and health — which determined they were marijuana users. Survey respondents were asked if they ever used marijuana, and, if so, when they first tried the drug; data on cigarette use was also collected. This data was cross referenced with mortality data from 2011 from the National Center for Health Statistics to determine if participants from NHANES died during the study period.

The findings revealed 73 percent of the participants were still alive; about 35 percent reported no marijuana use or tobacco; 21 percent used only marijuana, but no tobacco; and 16 percent marijuana or tobacco currently, but smoked cigarettes in the past. Compared to people who didn't smoke pot, those who did had a 3 times higher risk of death from high blood pressure during the study. No statistically significant links were found between marijuana use and the increased risk of death from heart disease or stroke.

"We found higher estimated cardiovascular risks associated with marijuana use than cigarette smoking," said Yankey.

Yankey and her colleagues believe their findings show marijuana use may carry even greater consequences on our heart health than those for cigarette smoking. The chemicals in tobacco smoke harm blood cells and damage heart function and the structure and function of blood vessels, increasing the risk of atherosclerosis. This is a disease in which plaque builds up in the arteries; atherosclerosis is a main contributor to the high number of deaths from smoking, according to the National Heart, Lung and Blood Institute.

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Previous research has found young men are more likely to experience a very particular heart problem after smoking pot. These smokers were known to have high rates of stress cardiomyopathy, which is a temporary weakening of the heart muscles that is often triggered by things like intense stress and grief. Out of over 33,340 patients with the condition, only 210 patients used marijuana, with the young men having fewer standard risk factors than the average, non-smoking group. This led the researchers to conclude marijuana is an independent risk factor for certain types of heart conditions.

But, like the current study, findings on marijuana use and heart health are extremely limited.

Study Limitations On THC's Effect On The Heart

In the University of Georgia study, researchers relied on participants to report their marijuana use, which can be unreliable. Moreover, the study had a vague definition of classifying a "marijuana user." For example, if participants answered "yes" when asked if they've ever smoked pot, they were considered a user without specifying frequency of use, or if a respondent continued to use marijuana throughout the study period.

In addition, the study only focused on recreational use, which means it's unclear whether the same effects would apply to medicinal users.

This study introduces marijuana's potential risk to heart health, but it's a small study that requires further investigation with a larger group.

According to Yankey: "With the impending increase in recreational marijuana use it is important to establish whether any health benefits outweigh the potential health, social and economic risks."

There is also limited evidence on whether smoking pot can affect those with a heart condition. THC does increase heart rate, which could be worrisome for those at high risk of heart failure.

Moreover, different marijuana strains may have a different effect on heart health. Strains higher in CBD and lower in THC may help address the issue of a racing heartbeat. For example, indicas can give a much more relaxed high, because they have a higher CBD content, which counteracts THC.

So, does marijuana really hurt the heart?

It depends.

Studies on healthy populations who smoke marijuana are inconclusive.

Undoubtedly, marijuana has some benefits to human health, such as pain relief, as the drug's recreational use is expanding across the U.S. But science tells us to slow down with marijuana legalization; our understanding of the drug’s health risks is still under investigation. Research on recreational and medicinal use and its health effects needs to be approached with caution and done thoroughly.

Source: Yankey BA, Rothenberg R, Strasser S et al. Effect of marijuana use on cardiovascular and cerebrovascular mortality: A study using the National Health and Nutrition Examination Survey linked mortality file. European Journal of Preventative Cardiology. 2017.

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