Is marijuana bad for your heart? Evidence is complicated – but doctors are concerned
About a dozen cardiologists are warning Americans to put down the lighter and give up smoking marijuana for good because of potential harm to your heart, lungs and blood vessels.
Although cannabis has therapeutic benefits for people dealing with muscle pains, nausea, opioid addiction and age-related diseases such as Parkinson’s, the American Heart Association said Wednesday that no known benefits exist for cardiovascular diseases, which it says involves many of the “concerning health implications” of the drug.
The group cites observational studies that have linked marijuana to increased risk of heart attacks, heart failure and heart rhythm disorder, while comparing the inhalation of cannabis smoke to that of a tobacco cigarette.
The report comes as marijuana use soars, especially among younger adults, and as its legality continues to make its way from illicit to legalized at the state level. However, many unknowns remain, such as the drug’s association with cancers and how differences in doses and delivery — smoking, vaping, eating, drinking — can mitigate potential harms.
“Overall, evidence is still inconclusive for cannabis use and adverse cardiovascular outcomes, resulting in an urgent need for carefully designed, prospective short- and long-term studies,” the doctors said in the report published in AHA journal Circulation. “Although small observational studies in older adults have reported improvement in affective symptoms such as depression and anxiety with cannabis use, the effects in adolescents and young adults are less clear.”
Study of marijuana has been limited because of its listing as a Schedule 1 controlled substance, meaning it’s illegal federally and labeled “as having no accepted medical use and a high potential for abuse,” according to the group.
Marijuana’s effect on the heart and blood over time
The AHA says some research has found that within one hour of smoking, THC — the high-inducing chemical in cannabis — could spark rapid heart rate, place a “greater demand” for oxygen by the heart, increase blood pressure and cause dysfunction in artery walls.
Another concern is the drug’s interaction with other medications such as blood thinners, antidepressants, antipsychotics, cholesterol reducers and antiarrhythmics. These relations are poorly understood because of a “dearth” of research on the long-term effects of marijuana use, the group said.
“Unfortunately, most of the available data are short-term, observational and retrospective studies, which identify trends but do not prove cause and effect,” Dr. Robert Page, chair of the writing group for the report and a professor of medicine at the University of Colorado in Aurora, said in a news release.
The way the drug is consumed could also influence how it affects the body, the doctors wrote. They cited research that showed smoking marijuana, regardless of THC content, increased concentrations of the harmful gas carbon monoxide and tar in smokers’ blood.
“Many consumers and health care professionals don’t realize that cannabis smoke contains components similar to tobacco smoke,” Page said in the release. “If people choose to use cannabis for its medicinal or recreational effects, the oral and topical forms, for which doses can be measured, may reduce some of the potential harms.”
Meanwhile, another active ingredient in cannabis called CBD, which does not cause a “high” in users, has shown opposite effects on the body: reduces heart rate, lowers blood pressure, reduces inflammation and increases the ability of arteries to open.
Still, the AHA doctors noted the potential for “impurities such as heavy metals, herbicides, pesticides and fungicides” in CBD products. They suggest people only use legal cannabis products and not those off the black market.
The group also said regular cannabis use at young ages may lead to structural changes in the brain that affect development.
Marijuana and cancer
Cannabis’ ties to different types of cancer have always been cloudy, largely because of “limited and conflicting evidence,” according to the group.
“Low-strength evidence suggests that smoking marijuana long term may be associated with the development of testicular cancer,” the group said in the report. “Findings for lung cancer are mixed and confounded by few marijuana-only smokers, poor exposure assessment, and inadequate adjustment within studies.”
It’s also unclear if heavy marijuana smokers are at risk for chronic obstructive pulmonary disease, “however, chronic bronchitis has been reported.”
