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• Posted September 28, 2023

Heavy Marijuana Use May Harm the Heart

People who abuse marijuana may be setting themselves up for heart problems down the road, Canadian researchers report.

The new study found that people with so-called cannabis use disorder may have a 60% higher risk for a heart attack, stroke or other major heart-related event, compared to those who don't abuse the drug.

"There appears to be a substantial association between cannabis use disorder and the increased risk of first-time adverse cardiovascular events," said lead researcher Dr. Anees Bahji, a clinical assistant professor of psychiatry at the University of Calgary, in Alberta. "Individuals who have been diagnosed with cannabis use disorder should be aware of this potential risk to their cardiovascular health."

The findings also highlight the importance of considering heart-related risks associated with cannabis use disorder, which may have been previously underestimated or overlooked, he said.

Bahji cautioned, however, that his study can't prove that marijuana abuse caused heart problems, only that people with cannabis use disorder might be at greater risk.

"Health care professionals should be aware of this potential risk when caring for patients with cannabis use disorder and provide appropriate guidance and monitoring," he advised.

Cannabis use disorder is a pattern of marijuana use that leads to clinically significant impairment or distress, Bahji explained.

Symptoms and behaviors related to cannabis use disorder include unsuccessful attempts to reduce or control use, spending a great deal of time obtaining or using cannabis, and experiencing withdrawal symptoms when not using it, he said.

"The diagnosis of cannabis use disorder depends on meeting specific criteria, and it is not solely based on frequency or quantity of use," Bahji said. "Individuals can develop this disorder even with relatively infrequent cannabis use if their use leads to significant impairment in their daily life, relationships or overall well-being."

How cannabis use may increase the risk of heart problems is not clear, he noted. Possible contributors include marijuana's ability to increase heart rate, blood pressure and inflammation in the body, and to affect blood clotting and the ability of blood vessels to dilate and relax, Bahji said.

"The relationship between cannabis use and cardiovascular events is complex and may also be influenced by factors such as the method of cannabis consumption, the presence of other co-occurring health conditions, and individual variations in response to cannabis," he said. "Further research is needed to better understand these mechanisms and the overall impact on cardiovascular health."

For the study, Bahji and his team cobbled together five databases that included nearly 60,000 cannabis users, half of whom had cannabis use disorder.

During eight years of follow-up, 2.4% (721) of people with cannabis use disorder experienced a first-time heart attack, stroke or another major heart event, compared with 1.5% (458) who did not have cannabis use disorder, the investigators found.

Dr. Peter Grinspoon, a primary care physician and cannabis specialist at Massachusetts General Hospital and Harvard Medical School in Boston, found fault with the findings.

"The presence of cannabis use disorder isn't very accurate in helping us to determine anything," Grinspoon said.

Cannabis use disorder might signify medical marijuana use so these people may have had other medical conditions that they were using the cannabis to treat, Grinspoon said. This could mean they were less healthy and could explain the higher rates of heart disease, he added.

"There are too many possible variables that could skew the results, so I don't make much of the study or its results. It is more anti-cannabis porn, in my humble opinion," he said.

"That said, if you take too high a dosage of cannabis, it can cause anxiety which, in turn, can trigger an arrhythmia [an irregular heartbeat] or possibly a coronary event, so, inpatients with a history of coronary disease, particularly recent, unstable coronary disease, or with a history of arrhythmia, I treat very carefully if at all with medicinal cannabis," Grinspoon said.

"Use becomes abuse when -- this has to do with my favorite definition of addiction -- you have continued use despite negative consequences," he said.

The findings were published Sept. 28 in the journal Addiction.

More information

For more on the risks of using marijuana, visit the U.S. Substance Abuse and Mental Health Services Administration.

SOURCES: Anees Bahji, MD, clinical assistant professor, psychiatry, University of Calgary, Canada; Peter Grinspoon, MD, primary care physician and cannabis specialist, Massachusetts General Hospital and Harvard Medical School, Boston; Addiction, Sept. 28, 2023