As marijuana legalization heats up the competition among vendors nationwide, some experts are warning about the sneaky side effects of smoking it.

Daily weed smoking could cause complications for heart health, according to a new study published in the Journal of the American Heart Association.

Researchers at the University of California San Francisco (UCSF) analyzed CDC data from 434,104 respondents to examine how cannabis use was associated with cardiovascular events.

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The impact of cannabis on the risks of having coronary heart disease, acute myocardial infarction and stroke were compared between those in the general adult population and those who had never smoked tobacco.

Of those surveyed, about 4% were daily cannabis smokers, 7.1% were non-daily users and 88.9% had not used any marijuana in the past 30 days.

Daily cannabis users had a 25% increased risk of heart attack and a 42% increased risk of stroke, the study found.

Cannabis use was associated with "adverse cardiovascular outcomes, with heavier use (more days per month) associated with higher odds of adverse outcomes," the researchers stated.

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Study co-author Dr. Abra Jeffers of Massachusetts General Hospital shared her reaction to the study findings with Fox News Digital.

"People think marijuana is harmless. It is not," she said. "We found that using marijuana (mostly by smoking) is as bad as smoking tobacco cigarettes."

"While we reported the results for daily use, any use increases risk — with more days of use per month associated with higher risk."

Recreational cannabis use is currently permitted in 24 states, according to a UCSF press release.

As of 2019, nearly 4% of Americans reported using cannabis daily, while 18% said they use it annually. 

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Senior study author Salomeh Keyhani, M.D., professor of medicine at UCSF, wrote in the same press release that "cannabis use is increasing in both prevalence and frequency, while conventional tobacco smoking is declining."

She added, "Cannabis use by itself might, over time, become the more important risk factor."

University of Colorado School of Medicine professor Dr. Robert Page serves as the American Heart Association chair for the statement on these findings.

In an interview with Fox News Digital, Page said the study is "unique" in that it looked at cannabis smokers separately from tobacco users.

"Cannabis is not an innocent bystander when it comes to cardiovascular health," he said.

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He emphasized the importance of the "safety signals" that have emerged from the study.

This includes the need for patients to be "more transparent" about their cannabis use with their health care providers, while providers should be "nonjudgmental."

He added, "There needs to be shared decision-making between the patient and the provider with regard to cannabis use. Patient-centered, non-judgmental conversations are what is really needed."

This is especially important if a patient has an underlying heart condition or has experienced a cardiovascular event while using cannabis without disclosing it.

What was "scary" about this study, Page said, is that most respondents were "fairly healthy."

The largest segment of daily weed smokers ranged from ages 18 to 34.

"Those are the individuals who typically don't go to their primary care doctor because they're young and they think they're invincible," he said. "And that’s what alarms me."

Many of Page's patients, who have the ability to smoke weed freely in the state of Colorado, assume that because it’s a natural substance, it "has to be safe," he said.

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"That is the farthest from the truth," he told Fox News Digital. "Cannabinoids have what we call psychotropic effects that affect your perception … and mental status. And like prescription medications that are psychotropic, they carry side effects."

Page added, "We do need to get out to the public the fact that there is a potential for these types of cardiovascular events and people need to make an informed decision."

The doctor said he's concerned that smoking weed will repeat the history of smoking cigarettes — the dangers of which took a "really long time to cement into public health."

Other cannabis consumption methods, such as edibles, were not a focus in this study, Page noted, adding that there is "not a lot of data" on the safety of those products.

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For people who use medical marijuana under the supervision of a physician, Page reiterated the importance of weighing the risks and benefits with the medical provider.

In a statement sent to Fox News Digital, the National Cannabis Industry Association pointed out that another study published by the American Heart Association in January 2024 found "no significant correlation between cannabis use and cardiovascular disease-related deaths over the last two decades, while alcohol was linked to 65% of deaths."

The organization said, "This report, along with many others, shows that while cannabis use is not entirely benign, it is clearly safer than alcohol."

It added, "Adult consumers in states with modern cannabis laws have the option to legally choose the safer substance, and it's time for federal law to catch up to those state laws."

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