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Heart risks of marijuana use need more research

Marijuana use could hurt the heart and blood vessels, according to a report that found no cardiovascular benefits to cannabis use and called for more research of the drug that is growing in popularity.

Cannabis studies have been limited because it is listed as a Schedule 1 controlled substance, defined by the U.S. Controlled Substances Act as having no accepted medical use and a high potential for abuse. A new scientific statement from the American Heart Association, published Wednesday in its journal Circulation, suggests the federal Drug Enforcement Agency remove cannabis from the Schedule I category so it can be widely studied by scientists.

Its use has risen over the past decade, especially among people 18-25. In all, 47 U.S. states, the District of Columbia, and 4 of 5 U.S. territories allow some form of cannabis use. Although many states have legalized medical and/or recreational use, cannabis growing, sales and use are illegal at the federal level, further complicating scientific research.

“We urgently need carefully designed, prospective short- and long-term studies regarding cannabis use and cardiovascular safety as it becomes increasingly available and more widely used,” Robert L. Page II, chair of the writing group for the statement, said in a news release. “The public needs fact-based, valid scientific information about cannabis’s effect on the heart and blood vessels. Research funding at federal and state levels must be increased to match the expansion of cannabis use – to clarify the potential therapeutic properties and to help us better understand the cardiovascular and public health implications of frequent cannabis use.”

Observational studies have linked the chemicals in marijuana to an increased risk of heart attacks, heart failure and a heart rhythm disorder called atrial fibrillation, according to the report.

A recent study cited in the statement suggests 6% of heart attack patients under age 50 use cannabis. Other research found users ages 18-44 had a significantly higher risk of having a stroke compared to nonusers.

“Unfortunately, most of the available data are short-term, observational and retrospective studies, which identify trends but do not prove cause and effect,” said Page, who also is professor in the department of clinical pharmacy and the department of physical medicine/rehabilitation at the University of Colorado in Aurora.

“Health care professionals need a greater understanding of the health implications of cannabis, which has the potential to interfere with prescribed medications and/or trigger cardiovascular conditions or events, such as heart attacks and strokes,” he said.

Although cannabis may be helpful for conditions such as muscle stiffness associated with multiple sclerosis, the new statement said cannabis does not appear to have any well-documented benefits for the prevention or treatment of cardiovascular diseases.

Some studies suggest cannabis — which contains the “high”-inducing THC (tetrahydrocannabinolic acid) and CBD (cannabidiol) — may be safe and effective for older populations. Though they are the least likely to use cannabis, older adults have used it to reduce neuropathic pain, common among people with Type 2 diabetes.

Researchers also have reported benefits for people with age-related diseases, including Parkinson’s and Alzheimer’s, but there is a dearth of research on the long-term effects of cannabis use among this population. One concern is the potential of interactions with other medications, including blood thinners, antidepressants, antipsychotics, antiarrhythmics for heart rhythm abnormalities, and statin drugs, which reduce cholesterol levels.

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