Weed has been on the receiving end of a PR campaign that for decades has painted it as a gateway drug, a substance that causes schizophrenia and promotes laziness, a plant that leads to a life of crime. As marijuana is legalized in more and more states, very few people are buying these arguments anymore. And as more and more parents use marijuana responsibly, the question has turned to more specific — and less concerning — health benefits and drawbacks of weed. Does smoking weed cause cancer? What are the risks and benefits of marijuana? All in all, is weed bad for you? Not entirely. But it’s also by no means an innocuous substance.
Medical marijuana is used to treat a wide range of conditions, from PTSD to chronic pain to multiple sclerosis. It may help you fall asleep and stay asleep. Yet for most people, the biggest and most obvious benefit of marijuana is, like a beer in the evening, some good old-fashioned dissociation. Stress relief is crucial for parents, and cannabis is safer than many other recreational drugs, including alcohol.
But weed isn’t harmless. When smoked, it can cause lung issues. Taken in any form, it can lead to pregnancy problems, impaired learning and memory, schizophrenia and psychosis, and more. Here’s what users and the pot-curious should know before diving in.
The Benefits of Weed
The biggest benefit of recreational weed is the high it gives. Compared to alcohol and other drugs, “it’s a much safer way to go home and relax without doing damage,” says Sarah Mann, a physician at the Mindful Medicine Clinic. “I’m a critical care physician with most of my time. And I see alcohol overdoses every single day, in every form. I have never had a cannabis overdose.” Sure, taking too much weed can make you uncomfortably stoned. But there are no recorded cases of lethal marijuana overdoses.
Cannabis can also improve some aspects of physical and mental health. “It’s particularly good for neurologic conditions, including pain conditions,” Mann says. Adults who use cannabis to treat chronic pain are less likely to experience symptoms of their condition, according to a comprehensive report from the National Academies of Sciences, Engineering, and Medicine. “Sometimes it can even be a definitive treatment,” Mann says.
Some people smoke weed for better sleep, which is probably effective — at least at first. There is “moderate evidence” that weed improves “short-term sleep outcomes in individuals with sleep disturbance associated with obstructive sleep apnea syndrome, fibromyalgia, chronic pain, and multiple sclerosis,” according to the National Academies report. But frequent use of medical marijuana is linked to issues falling asleep and staying asleep, according to a study of 128 people taking the drug for chronic pain. The researchers suggest that users may develop a tolerance to pot’s sleep-boosting benefits over time. And a recent large study found that people who had smoked weed in the past 30 days were more likely to get too much or too little sleep.
Another benefit of marijuana is its ability to help manage certain mental illnesses — particularly PTSD. It may also relieve depression, although more research on the subject is needed to be sure, according to a review of studies on medical marijuana and mental health. The National Academies found that cannabis may also aid adults with social anxiety. But regular use could increase the risk of developing the disorder.
For people who struggle with alcohol or opioid addiction, swapping those drugs out for marijuana could help with overcoming their substance use disorder, according to the mental health review. However, this technique is controversial, particularly because using weed increases a person’s risk of developing substance abuse of another drug.
How Is Weed Bad for You?
If you smoke weed, the biggest risk is to your lungs. Most research on smoking has been done on cigarettes, so researchers don’t know exactly how marijuana smoke affects the lungs. However, the American Lung Association is confident that smoking pot damages them. It injures the cell linings of the large airways and causes chronic bronchitis. It can also lead to chronic cough and phlegm production, according to the National Academies report.
A new study on the distinct effects of smoking pot found that long-term use leads to over-inflation of the lungs and increased resistance to airflow, more so than smoking tobacco does. Similar to with tobacco, smoking weed also makes it harder to extract oxygen from a breath.
It’s possible that smoking weed could increase the risk of developing lung cancer, but there isn’t enough evidence to be sure either way, according to a 2014 review. There is modest evidence to link only one kind of cancer to cannabis: a particular subtype of testicular cancer, according to the National Academies.
Marijuana could also harm the heart. Studies suggest that it could be linked to a higher risk of heart attack, heart failure, and atrial fibrillation, a type of arrhythmia that can lead to blood clots in the heart. One study found that people who use cannabis are 17 percent more likely to have a clot-caused stroke, and another found that they’re 24 percent more likely, according to a new scientific statement from the American Heart Association (AHA), published in the journal Stroke.
Weed doesn’t only pose a threat to the body, but also to the mind. Several studies suggest that pot can damage memory, learning, and attention. These effects stick around even after you quit. And the AHA statement says that weed can also give you a heightened sensitivity to stress. Additionally, some studies have found that marijuana-users have thinning in brain areas related to orchestrating thoughts and actions and decreased volume in areas related to memory, but other studied have not found these differences.
There’s also some truth in the schizophrenia scares from days past. Although using marijuana can’t cause schizophrenia, it does double the risk of developing schizophrenia in people who are vulnerable to the condition, according to a 2018 review.
Smoking pot could also add unnecessary health risks to parents’ future children — and may prevent them from having kids altogether. Cannabis can cause issues with sperm that lead to infertility. Using marijuana while pregnant could lead to lower birth weight, preterm birth, and a higher risk of autism. And people who used weed while pregnant had kids with more psychological issues and poorer cognitive functioning at age 9, according to the AHA statement.
Some people who smoke pot develop a condition called cannabinoid hyperemesis syndrome, or CHS for short. Only those who regularly use marijuana (daily or weekly) develop it. CHS is categorized by symptoms of nausea, vomiting, and abdominal pain that come and go in cycles, according to a 2011 review. It’s likely more common in men. Symptoms generally stop when you shelf the weed.
The Unknown Risks and Benefits of Marijuana
Because marijuana is illegal at the federal level, it’s difficult for researchers to study how it affects health. There are still many unknowns about how it could both hurt and help your body. Scientists won’t understand the full picture for many years.
“We know that cannabis could be used for many diseases, and, to some extent, we also know how it works. But the fact that there are so many products on the market also gives the impression that it helps with everything and nothing,” Tibor Harkany, Ph.D., a neurobiologist at the Medical University of Vienna’s Center for Brain Research, said in a recent press release. “But, in fact, cannabis is not a miracle plant; it has very specific uses and we urgently need a number of scientific, evidence-based clinical trials on this subject.”
In the meantime, the only people who can weigh the known risks against the benefits of marijuana are you and your doctor.