At this very moment, behind a high school storage shed or under the grim fluorescents of a strip-mall Wendy’s, a too-high teen is convinced they’re going to die. Eventually that teen will calm down, and probably thank their friend for refusing to call an ambulance when they’d begged them to. Getting insanely high for the first time—or getting higher than you’ve ever personally been, via oils or edibles or whatever—can be a frightening experience. You reassure yourself by thinking: no one has ever overdosed from smoking weed. But—wait. Do you know that? Have there not been exceptions? And is it possible that you’re one of them? Frantically you pull out your phone and Google: ‘Can you overdose from weed?’—and are brought right here, to this week’s Giz Asks, in which a number of experts in psychiatry, substance abuse, policy, and toxicology give their take on that very question. (The upshot, if you’re too fucked up to read: you’ll almost certainly be fine, eventually.)
Ryan Gregory Vandrey
Associate Professor, Psychiatry and Behavioral Sciences, Johns Hopkins Medicine, whose research focuses on the human behavioral pharmacology of Cannabis, among other things
The short answer is yes, you can overdose on cannabis. The nuance is this. An overdose does not necessarily mean death. From my perspective, an overdose means a several different things. In one case it means that you take a dose that is greater than you can tolerate or than you intended, and as a result you suffer unwanted adverse effects. Because there is such variety in the chemical content of cannabis products, because there are so many different formulations and routes of administration that can have differential rates of drug absorption, and because the product labeling can often be incorrect, it is not uncommon for even experienced cannabis users to get too big a dose and experience nausea/vomiting, paranoia, anxiety, dizziness, cognitive impairment, or other adverse events after using cannabis that are not typical or expected.
Another example of an overdose is adverse effects that result from product contamination. In the opioid world, when someone buys what they think is heroin, but they get fentanyl, and they stop breathing after using that product, we call that an overdose. In the cannabis world, there are examples of people buying what they think is cannabis or a hemp/CBD product, and it is contaminated with high potency synthetic cannabinoids, residual solvents from the extraction process, or other contaminants that directly cause severe health consequences. I call that a cannabis overdose.
The other scenario is when individuals with a pre-existing health condition or uncommon genetic make-up respond atypically to cannabis and suffer severe adverse consequences. There are cases where young, otherwise healthy individuals with few other risk factors experience major cardiovascular events such as myocardial infarction shortly after cannabis use, or experience an acute psychotic episode after an acute cannabis dose. These are not common, or typical reactions to cannabis, but there are an increasing number of case reports where it appears that cannabis is the likely cause of these events in a subset of the population, and in some cases the result is the death of the individual. I know that there is a very well accepted tenet that “you can’t overdose on pot” meaning that use of cannabis cannot kill you the same way use of cocaine, heroin, or alcohol can. From my perspective, use of cannabis is very unlikely to directly contribute to death, but it is possible. I also believe that most cannabis users have experienced an overdose, meaning that they had an experience where they were “too high”, and the drug effect was both unexpected and unpleasant. Within that realm, there is a range of severity of this kind of experience, and in most cases it is short lived and not clinically important. In a subset of individuals, however, the result of a cannabis overdose can have substantial negative consequences and there is no way of reliably predicting ahead of time for whom or when these experiences with occur. There are clear differences in the likelihood and severity of experiencing an overdose from using cannabis versus many other drugs (the risk factor favoring cannabis in most cases), but it is foolish to believe that cannabis use is benign and cannot result in an overdose.
Chelsea Shover
Epidemiologist and Postdoctoral Research Fellow in Psychiatry and Behavioral Sciences at Stanford University
Marijuana has essentially no fatal overdose risk, but non-fatal overdose is possible. Ingesting cannabis can lead to severe and life-threatening health consequences for children and infants. For adolescents and adults, an overdose can look like a more severe (and unpleasant) version of usual/desired cannabis intoxication. Symptoms can include confusion, paranoia, anxiety, panic, fast heart rate, delusions, hallucinations, increased blood pressure, and nausea or vomiting. These can land people in the emergency room, lead to unintentional injuries, or just make for a bad time.
Wayne Hall
Professor, Centre for Youth Substance Abuse, The University of Queensland, Australia, whose research
The conventional view (which I have publicly expressed) is that cannabis does not cause a fatal overdose. This statement is still true if the mechanism causing death is respiratory depression and probably still largely true if the form of cannabis is lower THC content herbal cannabis.
One nowadays has to be more cautious about claiming that cannabis cannot produce overdose for the following main reasons (1) reports of deaths due to cardiovascular disease in heavy cannabis users... which raise the possibility that high doses of THC could cause deaths (probably in persons with elevated CVD risk; (2) the rise of super potent cannabis concentrates with THC > 70% which if smoked in pipes or on nails could possibly amplify this cardiovascular risks; and (2) case reports of deaths in persons who use potent synthetic cannabinoids, i.e. synthetic drugs that act on the same cannabinoid receptors as THC.
My guess is that these types of death are rare but it would be unwise to continue to assert (as cannabinophiles are wont to do) that it is impossible to overdose on cannabis.
There is another sense in which people can and do overdose on cannabis, namely, they receive doses of THC larger than they intend which result in their seeking help, usually from a medical emergency department. These type of overdoses are not fatal. They involved users receiving large doses of THC that produce distressing experiences (e.g. intense anxiety or distress, psychotic symptoms or compulsive vomiting) that users do not enjoy. The frequency of this type of overdose in EDs has increased since cannabis legalization in Colorado. They seem to me more common when people use cannabis edibles because it is more difficult to titrate THC doses when cannabis is used by this route.
Senior Policy Analyst for Transform Drug Policy Foundation
In terms of a fatal or potentially fatal overdose—it’s not possible, simply because the fatal dose of THC is more than a person can ever realistically consume. You can get extremely sick, end up in hospital, and have a terrible time, but unless you have some other health vulnerability, like a heart problem, or do something stupid like driving, death is exceptionally improbable. The lower estimates, based on rather horrible animal LD50 tests, suggest consuming and absorbing over 50 grams of pure THC would reach a 50% lethality rate for an adult male—but other estimates put it much higher. You cant feasibly smoke anything like that much—although some people may try their best, and you would be hard pressed to consume it with conventional edibles; you would probably reach a fatal level of sugar or salt consumption before the THC got you. If you were really determined you could possibly inject enough pharmaceutical THC to kill you, but that’s an unlikely scenario for anyone, let alone the majority of social users.
If overdose is more broadly characterized as having more than intended or experiencing unpleasant, negative or adverse effects, even if temporary, then yes its absolutely possible, and fairly common. Controlling dosage is obviously the key. This sort of adverse event overdose is more likely if you are a novice or less regular user, and if you use stronger cannabis, especially concentrates, as these give a higher dose per inhalation making dosage is harder to control. Edibles are more often associated with such adverse events, especially for novice users, as the slow onset means precisely regulating dosage is difficult and unpredictable. Poorly dose controlled or labelled products can obviously increase the risks.
To avoid all risks, don’t use at all. To reduce risks, know what you are consuming, and use moderately in a safe environment. With edibles take a small amount first and leave it at least two hours and see how you get on before considering taking any more.
Jonathan P Caulkins
Professor, Operations Research and Policy, Carnegie Mellon University, and the co-editor of Marijuana Legalization: What Everyone Needs to Know
Whether one can overdose on cannabis depends on one’s definition of the word overdose. If overdose means any acute adverse health consequences of taking too much, then absolutely. There is no question cannabis can do that. If one means more narrowly death by the same physiological mechanism that is involved in opioid overdose (suppressed respiration, etc.), then no, that is not how cannabinoids work. If one means death by any mechanism, then the answer is contested but appears to be yes, but only in very rare circumstances. There are case studies of cannabis-related deaths via at least three mechanisms: (1) Tachycardia, (2) Passing out after dabbing and hitting ones head, and (3) Psychotic episodes inducing suicide. But even those who think such deaths can be causally attributed to the large dose of cannabis acknowledge that they are very rare events.
Paul Armentano
Professor, Science, Oaksterdam University, and the Deputy Director of the National Organization for the Reform of Marijuana Laws (NORML)
Unlike opioids and alcohol, cannabinoids are not central nervous system depressants and are incapable of causing lethal overdose—regardless of quantity or potency. States the National Cancer Institute, “Because cannabinoid receptors, unlike opioid receptors, are not located in the brain stem areas controlling respiration, lethal overdoses from cannabis and cannabinoids do not occur.” A 2017 US Drug Enforcement Administration publication affirms, “No deaths from overdose of marijuana have been reported.” For these reasons, the DEA’s own administrative law judge once determined, “Marijuana, in its natural form, is one of the safest therapeutically active substances known to man.”
Keith Humphreys
Professor, Psychiatry and Behavioral Sciences, Stanford University, and a former Senior Policy Advisor for White House Office of National Drug Control Policy under the Obama Administration
Non-fatal overdoses (more properly “drug poisonings”) happen all the time with cannabis products—usually it presents in the ER like a panic attack or sometimes as a psychotic episode in which the person has temporarily lost touch with reality. But I have never seen convincing evidence of a fatal cannabis overdose. Maybe it’s remotely possible, but it’s remotely possible to be killed by a meteorite falling from space too and I wouldn’t suggest anybody spend time worrying about that.
Dazhe Cao
Assistant Professor of Emergency Medicine and Program Director of Medical Toxicology at UT Southwestern Medical Center and Medical Director of the Toxicology Service at the Parkland Health and Hospital System
To answer the question of whether you can overdose from marijuana, I have to clarify the terminology. Marijuana describes the dried plant material of Cannabis sativa. The recreational use of marijuana and other cannabis-derived products results from psychoactive properties of Δ9-tetrahydrocannabinol (THC). Over the last decade, THC concentrations in marijuana and other cannabis products have dramatically increased. Chandra et al found that US marijuana THC concentration increased from a mean of 6% in 2008 to 9.4% in 2017. Concurrently, sinsemilla (a specialized growing method of Cannabis sp.) THC concentration increased from a mean of 11.5% to 17.8%, and hash oil (THC concentrates) increased from a mean of 6.7% to 55.7%. Furthermore, the standard deviation around the mean of 55.7% in hash oil was 24.7%. We have seen concentrates of nearly 100% THC. One of the adages in medical toxicology is “the dose makes the poison.” With regards to the type of cannabis product used, one should not equate the risk of overdose from 9% marijuana with that of 100% THC oil.
The second point of clarification revolves around the word “overdose.” Adverse or unintended effects from acute cannabis use is common. Of the 253 cases of acute cannabis exposure reported to the Oregon Poison Center from December 2015 through April 2017, only 16 (6.3%) cases remain explicitly asymptomatic or 93.7% of cases “overdosed” on cannabis. Although the percentage of cases cannot be generalized to the public, majority of whom achieve the intended euphoric effects of THC, we can see that people can have unintended effects from cannabis use. However, when one uses the word “overdosed” to imply fatality, death resulting from isolated acute cannabis exposure is rare. Cases of cannabis-related death have been reported in the literature - one pediatric case of possible cannabis-associated myocarditis, one traumatic death, and numerous cardiovascular deaths. Typically, death associated with cannabis use involves other predisposing factors like trauma or underlying cardiovascular disease. In children, respiratory depression can be life-threatening and may require mechanical ventilation. In comparison to the respiratory depression from the opioids like heroin or fentanyl, the risk from cannabis exposure is far smaller.
In summary, one can overdose from cannabis products, but risk of death from isolated cannabis use is low, especially from “lower” THC-concentration marijuana.
April D. Thames
Associate Professor of Psychology and Director of the Social Neuroscience in Health Psychology Lab at USC Dornsife
The idea of fatal overdosing hasn’t been supported in clinical settings as well as the scientific literature. There are cases where people take too much marijuana, which we know can result in paranoia, confusion, and rapid heart rate. If someone had a pre-existing physical condition, such as cardiovascular problems, and were then to ingest a high dose of marijuana, it’s conceivable that they could experience a fatal overdose—but that’s in the context of a pre-existing physical illness. But the risk for fatal overdose in the way we think about it with other drugs—there’s not enough evidence to support that happening.
That said, with legalization, and the popularity of edibles, there have been more and more cases of people showing up to the ER with these symptoms, where they may report that they feel like they’re dying but they’re not actually overdosing in a fatal way.
I study the cognitive effects of marijuana for people who are heavy users over many, many years. These are people who started very young—their age of onset was preteen or teenage years, and they’ve used heavily throughout their lifetime. With these specific users, we do see some deficiencies in certain cognitive areas. But for someone who decides to try marijuana for the first time, or even a recreational, once-in-a-while-type user, typically any cognitive effects will reside as soon as the drug is out of their system.
There definitely does need to be more research in this area, because now we have so many different concentrations and strains, which makes it very hard to know what the long-term effects are, particularly with THC, the psychoactive ingredient, which tends to be associated with more adverse consequences (whereas cannabidiol, or CBD, has a more sedative effect and actually has been shown in some studies to have benefits on the immune system).
Karen Corsi
Associate Professor, Psychiatry, University of Colorado
The question of whether one can overdose on marijuana has come up in many academic and lay forums recently due to changing marijuana policies in many states nationwide and thus a corresponding increased interest and consumption of marijuana. To my knowledge, there have been no cases where a person has actually died from overconsumption of marijuana alone. The typical definition of overdose leads one to think of death by opiate overdose or other extreme emergency situations where a person needs life-saving medical measures to survive the event. This simply does not happen with marijuana. While it is possible for someone to consume too much marijuana and suffer ill health effects such as paranoia, hallucinations, and in some cases psychotic symptoms, among others, there is not a threat of death by consumption of marijuana alone. Treatment for overconsumption of marijuana is simply to wait until the effects subside, which could be a matter of hours. And while this situation of consuming too much marijuana may be very uncomfortable emotionally and even physically, there is not a corresponding physical risk of death.
Matthew Fadus
General Psychiatry Resident at the Medical University of South Carolina
Ongoing legal changes and more widespread acceptance and tolerance of cannabis use have led to more and more questions related to cannabis use and this is certainly one of them. Cannabis use has become so common and tolerated and therefore we would expect a much higher rate of suspected overdoses, which fortunately has not been the case. Cannabis is not something that we think of as having a mechanism that can directly lead to death as a result of too high of a dose. But it is also important to define the term “overdose” as well. In psychiatry we often think of “overdose” as an intentional attempt to end one’s one life, whereas others may view it more to suggest an undesired outcome or excessive or dangerous use.
With that being said there are certainly problematic effects of using too much cannabis or using stronger strains of cannabis. The most concerning ones that we see in psychiatry include psychotic episodes which can be quite distressful, including paranoia as well as auditory and visual hallucinations. There are other more common adverse effects of cannabis use which can include including nausea, vomiting, headache, memory concerns etc., however these by no means are necessarily dangerous in terms of overdose potential.
The more common drugs that are concerning related to overdose (if we define it by intention to harm oneself) would be those such as opioids (oxycodone aka Oxycontin and heroin) because they lead to excessive sedation and suppress the parts of the brain that are responsible for breathing. Opioids can be particularly dangerous in terms of overdose when combined with other sedating medications that can reduce our respiratory drive, such as benzodiazepine medications (i.e. alprazolam aka Xanax , and clonazepam aka Klonopin). Other substances such as stimulant drugs (i.e. cocaine) can cause death by disrupting the electrical activity of the heart or limiting blood flow and function of the heart. Cocaine use causes a massive release of the body’s “fight or flight” chemicals which can cause significant arrhythmias in the heart.
Fortunately, the effects of cannabis do not lead to respiratory suppression like opioids nor are they as concerning related to the cardiotoxic effects of cocaine. However, many people can attempt and unfortunately be successful in their intentional overdose with more than one substance (i.e. complete suicide by using cannabis and opioids) which can conflate the issue. It is generally accepted that although cannabis use can become problematic and lead to adverse effects in high doses and frequencies, there is not a concern for overdose death directly related to cannabis use.
Sharon Levy
Director of the Adolescent Substance Use and Addiction Program at Boston Children’s Hospital
Yes, you can overdose on marijuana. Reports of over sedation and respiratory depression secondary to marijuana ingestion have been reported in young children who have consumed very large amounts of THC relative to their body size. This is less likely to occur in larger adults. There have been cases of children admitted to intensive care units but to my knowledge, no deaths have been reported.
Non-lethal overdose on marijuana, resulting in acutely altered mental status is pretty common, and more closely associated with consumption of edibles. There have been accidental deaths related to this phenomenon, though marijuana per se is not the proximal cause of death. A recent publication in the Annals of Internal Medicine analyzed the rates of ED presentation among users of edible marijuana users and may be of interest in answering your question. In my clinical practice I hear about “green outs”—essentially consuming enough marijuana to result in acute neurotoxicity causing memory loss—regularly. This phenomenon is “under the radar” because users often do not present to the emergency department and so there is no good data on how common it is. While these events are far less lethal than opioid overdose, they are not all benign.
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