Most people are unaware that cannabis (marijuana or “weed”) can be addictive and that regular use carries health risks such as stroke, heart attack, and mental illness, among others. Medical marijuana users may take the drug frequently or daily for chronic pain, and frequent users are more likely to experience health problems. Yet most Americans see little problem with marijuana use.

In the United States, 22% of Americans ages 12 and older, or 19 million people, used cannabis in 2022, with the highest use among 18- to 25-year-olds (38%). In 2022, 30.7% of 12th graders reported using cannabis in the past year, and 6.3% have consumed cannabis daily in the last 30 days.

Cannabis use disorder (CUD) is also on the rise, with 5.7 million people meeting diagnostic criteria for this disorder in 2022. Risk was highest among young adults ages 18-25 (16.5%). The core feature of the disorder is that users are unable to stop using despite cannabis’ negative consequences. Some people with CUD smoke marijuana several times a day, and many users are young men.

Marijuana is increasingly available in the United States, with 38 states allowing adult use of “medical marijuana” and 24 states allowing adult recreational use of cannabis. However, marijuana is classified as an illegal Schedule I drug (along with heroin and LSD) by the Drug Enforcement Administration (DEA). Although there is widespread support for decriminalizing cannabis, the federal government generally looks the other way when it detects marijuana use in states that have legalized marijuana.

It is also important to know that the effectiveness of today’s cannabis very different from the product your grandparents might have used in the 1960s or 1970s. Modern marijuana products, for example, average 15-20% tetrahydrocannabinol (THC, the psychoactive component of cannabis), with some products advertising 90% THC. In contrast, the average THC content of marijuana smoked in Woodstock in 1969 was less than 1% THC.

The Yale School of Medicine recently announced that the Yale Center for the Science of Cannabis and Cannabinoids will study the acute and chronic effects of cannabis and cannabinoids on human neurodevelopment and mental health. This organization is led by international expert Deepak Cyril D’Souza. He noted: “Besides the plant, there is an amazing variety of other cannabis products with even higher THC content, such as dabs, oils and edibles – some with up to 90%.”

Synthetic cannabinoids (SCs) are even more serious. They target the endocannabinoid system in many body organs and can interfere with the normal functioning of the brain and body systems. SC-related side effects are mediated by the activation of cannabinoid receptors 1 (CB1R) and 2 (CB2R) and lead to harmful changes in the brain and body.

.Cannabis use disorder

Many people use cannabis without side effects. For some, however, the health risks associated with cannabis are real. About two-thirds of people diagnosed with CUD have at least one other substance use disorder, most commonly related to tobacco or alcohol. About half have a psychiatric disorder—most commonly posttraumatic stress disorder (PTSD), major depression, or generalized anxiety disorder. Having a psychiatric disorder is associated with more severe CUD.

Adolescents, young people and cannabis psychosis

The link between cannabis use and psychosis has been known for more than 100 years. Adolescents who smoke marijuana at least once a month are more likely to report hallucinations or paranoia than those who smoke once or twice a year. Epidemiological studies and, more recently, genetic studies suggest that cannabis use is a risk factor for later development of psychosis. The link is complex and factors such as use during adolescence, THC dose, past trauma and other environmental risks, and psychiatric symptoms such as anxiety and depression can accelerate the process.

Stronger cannabis and more frequent use contribute to higher rates of psychosis, particularly among young people. Experiencing a cannabis-induced psychotic episode increases a person’s chance of developing bipolar disorder or schizophrenia by almost 50%, significantly higher than experiencing a psychotic episode triggered by amphetamines, hallucinogens, opioids or alcohol.

Consider others Health risks of cannabis

Because cannabis has been widely used for years without FDA approval, many believe it to be safe. Unfortunately, recent studies show that cannabis use can lead to cardiovascular disease, lung disease, cancer, asthma, anhedonia, and mental disorders. Gallagher et al. studied 4,101,362 patients from a 90 million patient cohort in the TriNetX healthcare system from 2004 to 2024 and just reported on a large, real-world study linking a diagnosis of cannabis use disorder and head and neck squamous cell carcinoma (HNSCC) with hazard ratios of more than threefold, a magnitude seen with other potent carcinogens associated with HNSCC, including alcohol.

Cardiovascular and stroke risks

Cannabis consumption often leads to increased heart rate in healthy people. Frequent cannabis consumption can also significantly increase the risk of heart attack and stroke. A study conducted in Journal of the American Heart Association studied nearly 435,000 American adults to investigate the link between cannabis and cardiovascular events.

The study found that daily use of cannabis – primarily through smoking – increased the risk of heart attack by 25% and stroke by 42% compared to not using the drug. Even less frequent use was associated with increased risks. Weekly use increased the risk of heart attack by 3% and stroke by 5%.

Cardiologists warn that drug use has sobering consequences for the cardiovascular system, especially in patients with undiagnosed cardiovascular problems. “Today, more and more young people with no apparent heart disease are coming to the emergency room with heart attacks,” says Yale’s D’Souza. Many emergency room visits occur within an hour of cannabis use.

Cannabinoid hyperemesis syndrome

Cannabinoid hyperemesis syndrome (CHS) is a form of cyclic vomiting often accompanied by abdominal pain. It can occur during or within 48 hours of frequent and heavy cannabis use. CHS is a leading reason for cannabis-related emergency room visits.

The condition can also occur in people who mistakenly believe that edible marijuana (such as in gummy bears or baked goods) has the same rapid effects as smoked marijuana. For example, a person may consume cannabis orally without feeling any effects for several hours and then eat additional edibles, causing digestive toxicity.

Surgical risks

Patients should tell a surgeon and anesthesiologist if they use marijuana. The American College of Surgeons notes that marijuana can affect the amount of pain medication needed after surgery. Additionally, surgeons may have difficulty placing a breathing tube needed for anesthesia in regular marijuana users. Frequent use of the drug can also cause breathing problems such as bronchitis. Surgeons recommend stopping marijuana use at least 72 hours before surgery.

psychosis

For more than two decades, Dr. D’Souza has studied the link between cannabis use and psychosis. Cannabis can trigger short-term psychotic disorders (cannabis-induced psychotic disorder, CIPD) that last from days to weeks. This condition often requires clinical intervention. In Denmark, increasing potency of cannabis is associated with an increased incidence of CIPD. Interestingly, up to 50% of patients diagnosed with CIPD were re-diagnosed with schizophrenia or bipolar disorder years later, suggesting that CIPD may predict chronic psychotic disorder. Researchers also point out that the risk of CIPD increases with more frequent and heavier use of the drug and with stronger cannabis potency.

Treatment of cannabis use disorders

The FDA has not approved any drug to treat CUD. However, GLP-1 drugs currently used to treat type 2 diabetes and obesity may help. A recent study suggests that semaglutide (Ozempic, Rybelsus, Wegovy) may reduce the risk of cannabis use disorder. The CUD recurrence rate was only 13.0% in patients who received semaglutide, compared to 20.4% in patients who did not receive it. That’s a 38% lower risk with semaglutide treatment.

Diploma

As cannabis becomes more widely available, people need to be aware of the potential risks associated with smoking cannabis, use by teens and young adults, regular use of the drug, and products with high THC content. Note that cocaine is considered safe and effective for ENT surgery, and fentanyl for pain relief and as an anesthetic. Marijuana and cannabinoids can also have benefits. A specific, FDA-approved medical use prescribed and supervised by medical specialists is one thing; we learned the opposite from the cocaine epidemic of the 1980s and the current crisis of deaths from fentanyl overdoses. Still, users need to be aware of the health risks and remember that self-medication carries additional risks. It was physician Sir William Osler, one of the founders of Johns Hopkins Hospital, who first noted: ““A doctor who treats himself has a fool for a patient.” Even a patient who treats himself should be aware of this.