Is Marijuana As Safe As We Think? Experts Reveal What’s Still Largely Unknown

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Cannabis: Is It Really Safe? Experts Tell Us What We Still Don’t Know

There are still a lot of things we don’t know about cannabis safety in humans, even though it’s becoming more famous and is said to be good for your health.

Not too long ago, anti-drug campaigns and sensationalised ads of teenage drug dealers luring their friends to ruin made marijuana look like the bad guy in the story of American drug policy. Since 1996, when cannabis was legalised for medical use in California and later for recreational use in many other states, the devil’s lettuce has lost its scary image and is now getting more and more support from the public. According to a Gallup study from 2023, seven out of ten Americans think marijuana use should be legalised. The percentage of adults aged 35 to 50 who used cannabis hit an all-time high of 28% in 2022, up from 13% the previous year.

Support comes from marijuana’s long list of supposed health benefits, such as lowering worry, relieving chronic pain, and helping people with mentally crippling conditions like PTSD. This image that makes “Mary Jane” seem like a miracle drug has quickly made it popular and in high demand.

In spite of this, there isn’t much proof that marijuana is safe for humans. New study actually shows that using cannabis, whether for medical or recreational reasons, greatly increases the risk of bad heart events like heart attack and stroke, and it also hurts brain development in teens and, to some extent, adults. Researchers have also found that marijuana can make men less fertile and may weaken the immune system.

Does this mean that all ways of using weed are bad? A psychologist at the University at Buffalo and the head of its Centre for Cannabis and Cannabinoid Research, R. Lorraine Collins, says that might not be the case. Collins tells Inverse, “It’s a very hard question.” “One thing I want people to know is that this is not a yes or no question.” Cannabis has a lot of different effects.



Cannabinoids are the name for more than 100 chemicals found in marijuana. Cannabidiol (CBD) and tetrahydrocannabinol (THC) are the two most well-known. There are different ways that these two chemicals affect your body. THC is what makes marijuana addictive, while CBD does not. Researchers used to think that CBD balanced out or counteracted the bad effects of THC, such as making people anxious and paranoid. But new research from the last few years shows that might not be the case. At least when using cannabis, high doses of CBD stop THC from breaking down, which makes the effects of the drug last longer.

People think that these cannabinoids work with the endocannabinoid system (ECS), which is an old cell signalling network that’s important for keeping the body and brain in balance. In the late 1980s, receptors for this system were first found. At the same time, it was found that our bodies make cannabinoids naturally. These are called endogenous cannabinoids, or endocannabinoids.

Some studies have shown that cannabinoids like CBD and THC may be helpful for health. For instance, cannabis may help treat or stop the sickness and vomiting that come with some cancer drugs. Doreganol is a name for a synthetic THC that was allowed by the U.S. Food and Drug Administration in 1985. Early research in the form of lab and clinical studies as well as personal accounts suggested that marijuana may help people control their seizures. In 2018, the FDA approved Epidiolex, an oral solution for severe seizures that contains CBD (which can be found in hemp, a type of cannabis).

When someone has a disease like chronic pain, it’s not always clear if marijuana is helpful. According to two systematic reviews published in 2017 by the journal Annals of Internal Medicine, there wasn’t enough scientific evidence to show that cannabis could help with neuropathic pain or treating PTSD.

A professor at the University of Colorado Anschutz Medical Campus and an expert in both clinical pharmacy and physical medicine, Robert Page, says that the fact that there isn’t any solid evidence is a good example of where marijuana study is right now.

Page tells Inverse, “The problem is that a lot of the data that are published are retrospective, which means they are based on old data.” “For the average person, that means I can say with certainty that 95% of the time, this is just an association and not always a cause.”

Collins and others from different universities made a report for the National Academies of Sciences, Engineering, and Medicine in 2017 that looked at thousands of cannabis studies and found that there was a huge gap in what was known about the risks and benefits of cannabis use.

An employee holds bottles of Epidiolex, a cannabinoid-based medicine, at the GW Pharmaceuticals Plc facility in Sittingbourne, U.K. The country is the biggest producer of cannabis for medical and scientific purposes, according to the United Nations.BLOOMBERG/BLOOMBERG/GETTY IMAGES




Collins says that this big gap is caused by the fact that there haven’t been many studies on humans. This is because marijuana is still in Schedule I, which is a group of drugs that are illegal and includes heroin, lysergic acid diethylamide (LSD), and ecstasy.

“[Federal regulations] have made it very hard to do research on humans. Instead, the studies are done on animals, especially in areas like how cannabis affects the unborn child,” she says.


All of the experts Inverse talked to for this story said that cannabis could be very helpful for some people, based on their specific medical needs. But right now, saying that using marijuana is safe is not taking into account all the warning signs that have shown up so far or the unknowns about short- and long-term use. This is especially true if it’s vaped or smoked.

“It seems to me that we’re putting the cart before the horse,” says Deepak D’Souza, a psychiatrist and director for the Science of Cannabis and Cannabinoids at the Yale School of Medicine. “States are selling it without the necessary evidence to support [its use].”

Several studies have found links between cannabis and a wide range of heart diseases that are both painful and could be fatal. A study published in the Journal of the American Heart Association in 2024 found that people who smoked, vaped, or even ate marijuana had a much higher chance of having a heart attack or stroke, even if they didn’t have a history of heart problems. The study found that both daily and occasional cannabis users had a higher risk of heart attack and stroke compared to people who didn’t use cannabis. The daily users’ risk of stroke went up 42% and their risk of heart attack went up 25%.
“The problem is that there aren’t any cardiovascular benefits to cannabis right now.” Page says, “We have no data to back that up at all.” Instead, these heart problems are usually bad side effects that happen when cannabis is used to treat other conditions like pain or nausea.

According to a study from 2022, the use of cannabis by teens and young adults has grown by as much as 245% since 2000. This has experts very worried about how the drug affects the brains of both adults and children. Teenagers who use marijuana regularly have different brain connections and less brain volume in areas that help with cognitive and executive processes like memory and impulse control. (This makes sense since a teen’s brain is still growing.) Some studies on adults have found no significant structural changes in the brains of cannabis users compared to non-users. Other studies that looked at people who had used marijuana for a long time found that the drug can make it harder to think and remember things. What made this different was the age at which the person started using, how much they used, and how often they used.

Smoking marijuana, regardless of the manner smoked, can scar and damage the lungs, according to the Centers for Disease Control and Prevention.PICTURE ALLIANCE/PICTURE ALLIANCE/GETTY IMAGES

Pot might even change our genes and defence systems. A 2023 study in the journal Molecular Psychiatry found that both short-term and long-term marijuana use was tied to changes in epigenetics, the study of chemicals that control which genes are turned on or off. The study discovered that these epigenetic changes were similar to those caused by smoking. These changes were linked to biochemical pathways that help cells grow, hormones send signals, the body fights off infections, and mental illnesses like schizophrenia and drug abuse disorder. One thing that should be noted is that this study did not link these epigenetic changes to any real health effects.

If you’re trying to get pregnant, taking a treat every day might affect your chances. A study from 2022 in the journal Fertility and Sterility by researchers at Oregon Health and Science University found that healthy nonhuman primates that were given a THC edible every day for 11 months (the same amount that humans take) had lower testosterone levels and testicles that shrunk by almost half. It wasn’t clear if those changes would last, but a follow-up study in 2023 showed that the animals’ effects got better after they stopped using THC. There is also some proof that THC may change monkeys’ menstrual cycles, making it harder for them to ovulate normally.

There is also the higher risk of psychosis and addiction that comes with high-potency weed, which was found in a study published in The Lancet Psychiatry in 2022.This is especially scary because the average amount of THC in weed sold today is much higher than it was in the 1970s. Thanks to advanced breeding methods, it has gone from having less than 2% THC to having 15% or more. D’Souza says that THC levels can be as high as 90% in some concentrated goods today, such as oils, edibles, and shatter, which is a cannabis extract that looks like glass.

Cannabis dispensaries in states like New York City are contributing to the boom in retail marijuana.GLASSHOUSE IMAGES/SHUTTERSTOCK

Even with all of these unknowns, people are not likely to stop using marijuana any time soon. According to a study from 2024, the cannabis market was worth almost $30 billion in 2022 and will be worth almost $83 billion by 2027. Experts say that loosening government rules that make it hard for scientists to do their work is needed to keep up with this fast-growing market and come up with a system of safety nets. That way may be getting more attention: President Joe Biden asked for a review of marijuana laws in 2022.Then, a year later, the U.S. Department of Health and Human Services (HHS) asked the U.S. Drug Enforcement Administration (DEA) to think about making cannabis a Schedule III drug, which has fewer restrictions. In February, NBC News said that the DEA would likely make an official decision soon.

Page thinks that the best way to raise knowledge is to understand that people use marijuana for different reasons, like medical or recreational purposes, and not judge their use.

Page says, “As health care professionals, it’s our job to let people know about possible risks and dangers, and that’s what I try to do.”


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