NEW YORK (CBSNewYork) — Various versions of medical and recreational marijuana are now legalized in all but seven states. That has led to much more research into the health effects of cannabis.

CBS2’s Dr. Max Gomez has more on new studies that show surprising heart effects in young users.

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For decades, it was thought that marijuana use could not lead to a physiologic dependence on cannabis, the active ingredient in the plant. But today’s marijuana isn’t what your parents smoked at Woodstock. It is far more potent.

“It felt as if my heart was going to explode out of my chest,” user Mike Stroh said.

Stroh said he smoked pot nearly every day for 15 years in Canada, where it has been legal for medicinal purposes for two decades, which explains why there is significant Canadian research into health effects of cannabis.

Now, a large peer-reviewed study found that while the risk remained low, those aged 18 to 44, who used cannabis at least four times a month, had nearly double the risk of heart attack over non-users.

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And now the news is worse for those classified as having cannabis use disorder.

“These are individuals who use cannabis with a frequency that has an impact on their functional abilities, how they’re functioning at home, at work, in relationships, at school,” Dr Alexandra Straytner said.

A new analysis presented at the American Heart Association Scientific Sessions found that, overall, 4.1% of patients hospitalized for heart attacks also had cannabis use disorder, and the proportion nearly tripled from 2.4% in 2007 to 6.7% in 2018.

“That doesn’t necessarily mean that cannabis use or cannabis use disorder causes cardiovascular incidents such as heart attacks. It may. It could also mean that there are other factors associated with cannabis use that increased risk for heart attack,” Straytner said.

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The study didn’t control for those other factors, such as use of other substances such as tobacco, alcohol or cocaine. Lifestyle factors such as diet and little physical activity could also be responsible. That’s where future research will focus.

Dr. Max Gomez