Can you overdose on weed?

Stories about a supposed first-ever lethal cannabis overdose occasionally crop up. They’re usually followed by rebuttals that no, you can’t die from weed overdose—and dying from another cause while having THC in your system is not quite the same thing.

According to the National Institute on Drug Abuse (NIDA), there has yet to be a drug overdose death solely attributed to cannabis. The Centers for Disease Control and Prevention also states that while symptoms of too much THC might include extreme confusion, emotional distress, increased blood pressure, heart rate, severe nausea, or unintentional injury, “a fatal overdose is unlikely.”

The statistics back this up. Cannabis is the most commonly used illicit drug in the US, despite being cleared for recreational use in more than a dozen states and territories. More than half of US adults have tried it in their lifetime and nearly one in three teenagers report having used marijuana in the past year, according to 2022 NIDA statistics. In 2021, 52.5 million Americans above the age of 12 reported using marijuana in the past year—which, according to rudimentary statistics, would have resulted in dozens of fatalities if the odds of blazing yourself to death was even one-in-a-million.

“Whether you can die from an overdose of marijuana, the answer is no,” says Alex Manini, an emergency medicine clinician specialist and toxicology expert at Mount Sinai Hospital in New York. But can someone non-fatally overdose on weed?

Symptoms of a weed overdose

Technically, an overdose happens any time someone takes more than the normal or recommended amount of a substance or drug. People show up in emergency rooms all the time after taking THC, Manini says, with all kinds of serious symptoms: panic or anxiety attacks, passing out, rapid heart rate, and even cannabinoid hyperemesis syndrome, an increasingly common condition marked by continuous vomiting.

“You (can) think of taking a hit as a therapeutic dose, to get a feeling of euphoria, maybe the giggles,” Manini explains. Or you can smoke so much that you feel like you need to go to the hospital. “I would call that an overdose. Will you die, if you’re a young, healthy person? Probably not.”

Cannabis is still a Schedule I drug, according to the federal government, and technically doesn’t have any currently accepted medical uses. Still, numerous states have moved to legalize marijuana for recreational or medical treatment (mostly for conditions such as cancer, HIV/AIDS, multiple sclerosis, glaucoma, seizures, epilepsy, and chronic pain). A 2016 analysis of samples from materials confiscated by the Drug Enforcement Administration over two decades also showed that the potency of THC in weed has increased at least threefold since 1995.

Altogether, this means that more people have more access to stronger cannabis. For most, that just increases your probability of getting higher than planned. But for some people, doctors say the advent of widespread, highly potent cannabis products increases their risk of an overdose.

[Related on PopSci+: The tasty chemicals flavoring the edible cannabis boom]

One group of at-risk individuals is children, who can accidentally ingest cookies, brownies, and other treats infused with super-concentrated THC doses, especially in states where recreational marijuana has been legalized. In a 2016 study in the journal of Clinical Toxicology, researchers investigated 430 calls to the National Poison Data System from 2013 to 2015 related to cannabis edibles and drinks. They not only found that the number of such calls increased year over year, but they also noted that a quarter of the cases involved children under the age of five, who, unlike adults, don’t know an ordinary looking treat might contain several doses of THC.

“That was a big finding,” says Dazhe Cao, a co-author of the study and a medical toxicology doctor at the University of Texas Southwestern Medical Center in Dallas. For those young children, cannabis exposure typically made them sleepy or uncoordinated, or affected their breathing (leading to intubation in two cases).

“That could [be a] potentially life-threatening situation for a child,” says Manini. Kids are not little adults—their bodies process all drugs differently than any older person’s would.

Other health concerns with cannabis use

Synthetic cannabinoids—human-made chemicals sometimes called Spice or K2—have also complicated the safety of all cannabinoids. When Manini and colleagues compared the clinical effects of synthetic weed with regular cannabis in 87 emergency department patients, they found those who ingested synthetic cannabis fared far worse, according to a separate set of results published in 2016.

“They had much worse cardiovascular effects, much worse agitation,” he says. The two products are chemically different, he explains, and so their safety should be considered separately. “The safety of marijuana has been borne out over decades. This is a whole new world.”

And even if weed itself won’t directly kill you, there have been deaths associated with cannabis products, Cao says. In a 2014 case, a 19-year-old Colorado man died after he ate a cannabis cookie, began behaving erratically, and jumped off a fourth-floor balcony. His autopsy reported marijuana intoxication as a chief contributing factor.

“It is very controversial to say whether someone can die from marijuana or cannabis products,” Cao says. “They’re not always direct causes of deaths.”

Cannabis use can also increase heart rate and blood pressure, and it can be a risk factor for some people who have pre-existing heart-related conditions, whether they know it or not. In one 2014 study published in the Journal of the American Heart Association, a group of French researchers examined 35 medical cases and concluded that cannabis could be a potential trigger for cardiovascular complications in young people. And when researchers from the Einstein Medical Center in Philadelphia analyzed a national database of patients in 2018, they found the prevalence of heart failure, stroke, coronary artery disease, and sudden cardiac death were significantly higher in patients with cannabis use. After adjusting for a number of factors including age, sex, diabetes, and tobacco or alcohol use, they found cannabis use remained an independent predictor of both heart failure and stroke.

Scientific evidence also links long-term weed smoking with chronic bronchitis and respiratory symptoms like coughing and wheezing. (There is not an established association between smoking weed and the incidence of lung or head and neck cancer). The long-term health effects of vaping weed remain mostly unknown.

[Related: Psychosis is the last marijuana side effect you should be worried about]

If you have pets at home, you might also be wondering how cannabis might affect them. For obvious reasons, the rise in edibles can pose a danger for your furry friends. Cats and dogs are increasingly exposed to THC-containing products, especially chocolate-containing treats, which has led to more cases of weed poisoning among pets. Because dog brains have more cannabinoid receptors than human ones, they could be more sensitive to the drug’s psychoactive properties, one 2018 study notes. (common symptoms of poisoning for dogs include lethargy, impaired balance, vomiting, and increased sensitivity to motion and sound). As seems to be the case with humans, synthetic cannabinoids may result in more severe symptoms for pets, such as tremors, aggression, and seizures. But to be clear, the authors state that “fatality in pets from marijuana intoxication is extremely rare,” and that no deaths associated with weed had ever been reported to Pet Poison Helpline.

All of this is not to say people should be wary of cannabis, Manini says—but they shouldn’t lump it in with other commonly used substances that regularly kill people. Thousands of Americans die every year from opioid overdose and alcohol poisoning, with rising rates among teens and young adults. Across the nation, most people over the age of 12 don’t see a great risk of harm from monthly cannabis use, according to statistics from the Substance Abuse and Mental Health Services Administration.

“It probably has a better safety profile than a lot of other illegal substances,” Cao says. “The perception that this is dangerous is dropping. But you can absolutely overdose.” Actually dying from that overdose, however, is far less likely—if at all possible.

This post has been updated. It was originally published on June 21, 2019.