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Surprising Side Effects of Marijuana, Say Studies

Science continues to uncover new information about marijuana's effects on the body.

In recent years, marijuana has seen major gains in mainstream acceptance. Today, pot is legal in 18 states, and more Americans report getting high than at any point in almost 40 years. Marijuana is now known to be a relatively safe drug. But, like any substance, it's not completely understood, and science continues to uncover new information about its effects on the body. These are some of the surprising side effects of marijuana, according to recent studies. Read on to find out more—and to ensure your health and the health of others, don't miss these Sure Signs You've Already Had COVID.


May Help You Lose Weight

stepping on scale

Seriously? Given pot's propensity to cause "the munchies," perhaps the most surprising recent discovery about marijuana is a 2019 study that suggests regular users are more likely to maintain a healthy weight. Researchers from Michigan State University looked at health data from 33,000 people and found that marijuana users are less  likely to be overweight or obese than non-users. Only 15% of "persistent" pot users were considered obese, compared to 20% of nonusers. "Over a 3-year period, all participants showed a weight increase, but interestingly, those who used marijuana had less of an increase, compared to those that never used," said the study's lead author, Omayma Alshaarawy, Ph.D., who acknowledged the findings are somewhat counterintuitive: "Our study builds on mounting evidence that this opposite effect occurs."

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May Impair Your Pancreas

Doctor in white medical lab coat points ballpoint pen on anatomical model of human or animal pancreas

Chronic marijuana use—defined as at least four times a week for more than three years—may reduce the ability of the pancreas to function normally, according to a study published last November in the journal PLoS One. Some people who use pot daily have developed without having risk factors for the condition. 

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May Make You Sick to Your Stomach

Young woman suffering from pain on bed

Marijuana is sometimes prescribed to relieve nausea, but some heavy users might experience the exact opposite effect. In cannabinoid hyperemesis syndrome (CHS), using cannabis can cause stomach pain, nausea and vomiting that can be severe. Experts estimate 2.7 million Americans experience the condition, which is frequently misdiagnosed. (CHS is so obscure that last year it was the subject of a "Medical Mysteries" column in the Washington Post.) "CHS went from being something we didn't know about and never talked about to a very common problem over the last five years," said Dr. Eric Lavonas, a spokesman for the American College of Emergency Physicians, in the New York Times

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May Cause Bronchitis

Man sneezing into his elbow.

Just like smoking tobacco, using marijuana involves inhaling smoke, which in some cases can cause bronchitis-like symptoms. "Marijuana smoke irritates the lungs, and people who smoke marijuana frequently can have the same breathing problems as those who smoke tobacco," says the NIDA. "These problems include daily cough and phlegm, more frequent lung illness, and a higher risk of lung infections." One important distinction: marijuana has not been found to increase the risk of lung cancer.

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May Affect Your Ability to Think and Plan

woman sit on couch hold laptop look in distance thinking distracted from online work

The popular image of the perpetually addled stoner who operates in a constant brain fog has faded as marijuana use has become more mainstream. But science has found there's some truth to the stereotype. In a new review of studies published in the journal Addiction, researchers analyzed health data from 43,000 people. They found that THC, the main psychoactive compound in marijuana, can negatively affect the brain's executive functions, including the ability to plan, organize, solve problems, make decisions, and control emotions. And to get through this pandemic at your healthiest, don't miss these 35 Places You're Most Likely to Catch COVID.

Michael Martin
Michael Martin is a New York City-based writer and editor. Read more about Michael