While prescription painkillers cause thousands of overdose deaths each year, no one has ever died from a marijuana overdose. But is it even possible to overdose on weed? The answer is no, according to the National Cancer Institute.
And here’s why:
“Because cannabinoid receptors, unlike opioid receptors, are not located in the brainstem areas controlling respiration, lethal overdoses from Cannabis and cannabinoids do not occur.”
In other words, marijuana and opioids affect different pathways of the body. Opioid pathways, also known as receptors, are present in areas of the brain that control breathing. As a result, taking too many painkillers can cause a person to stop breathing. But marijuana acts on a completely different set of pathways. These pathways are called cannabinoid receptors and they do not affect respiration. Thus, marijuana cannot cause someone to stop breathing, no matter how much they ingest.
It’s possible to die from opioid overdose or alcohol poisoning. But cannabis acts on the body and mind in a way that’s very different than opioids or alcohol. We’re all familiar with the tragic phrase “died of an overdose,” but when opioids like fentanyl, Oxycontin, or heroin are the cause, there’s a specific mechanism that leads to death. As Oxford University anesthesiology professor K.T.S. Pattinson has observed, “In drug addicts, respiratory depression is the major cause of death.” In other words, during an opioid overdose the victim falls unconscious and the body forgets to breathe. In some cases, an opioid overdose can also depress the brain’s mechanism that regulates the heart and blood circulation, leading to a drop in blood pressure and heart failure. Alcohol poisoning can become lethal when the alcohol overwhelms the liver’s ability to clear it, and alcohol in the blood anesthetizes those same brain systems that regulate breathing and blood pressure. They shut down, which leads to death.
What scientists call “the fundamental drive to respiration”—i.e., what tells the body to breathe—originates low in the brainstem, in an area known as the pre-Bötzinger complex. Opioids don’t just suppress pain and increase feelings of pleasure; they also depress the pre-Bötzinger complex, which causes breathing to become slow and irregular. In an overdose, breathing shuts down completely and death occurs due to lack of oxygen. Why doesn’t cannabis have the same effect? Because cannabinoids act on specific receptors that are not concentrated in the brainstem, where breathing and heart rate are controlled.
Cannabinoid receptors are most highly concentrated in the basal ganglia, the hippocampus, and cerebellum, which control cognition and movement. Those same receptors appear in scant numbers in brainstem areas like the pre-Bötzinger complex.
Another way of measuring a drug’s safety is by its therapeutic index. The therapeutic index is the ratio between a drug’s lethal dose and its therapeutic dose (amount that causes a therapeutic effect). Studies show that marijuana has a therapeutic index of 40,000:1. This means someone would have to take 40,000 times the normal amount of marijuana in order to die. Opioid-based painkillers have much lower therapeutic indexes. For example, the therapeutic index of morphine is only 70:1.
Lethal dosage is the point at which something will become so dangerous it could kill a person. And to figure out a substance’s lethal dosage, scientists use what they call the LD-50 formula.Basically, in an LD-50 test, scientists give a substance to small lab animals. They keep increasing the dosage until 50% of the test animals die. When that happens, that dosage becomes the LD-50, the point at which we assume it becomes very dangerous.
Good news for people wondering: can you overdose on marijuana. Scientists have tested its LD-50. Small test animals like mice and rats eventually reached incredibly high dosages at which they started to die. But in tests with larger animals, scientists never reached that point. They couldn’t find a lethal dosage for cannabis. It is estimated that marijuana’s LD-50 is around 1:20,000 or 1:40,000. In layman terms, this means that to induce death a marijuana smoker would have to consume 20,000 to 40,000 times as much marijuana as is contained in one marijuana cigarette.
Taking Too Much
It may be impossible to die by marijuana overdose, but that doesn’t mean you can’t take too much of it. Large doses of marijuana can lead to negative symptoms, such as agitation and paranoia. Cannabis itself cannot kill the human body. But let’s be clear: It is very possible to “overdose” on cannabis in the sense of overconsumption.
People tend to experience adverse side effects more when they eat cannabis rather than smoking it. The difference has to do with how our bodies metabolize cannabis. When you smoke weed, the THC and other cannabinoids enter your bloodstream directly through your lungs. But it takes a different route when you eat it. In that case, cannabinoids like THC are processed by your liver. This creates a slightly more delayed, and often more intense high. The other reason people tend to experience more adverse effects when they eat pot has to do with how people consume it. A lot of times, people eat an edible and expect to get high right away. When they don’t feel it as quickly as they thought they would, they eat more. And by the time it finally kicks in, they’ve eaten too much. The final result is a high that’s just too intense. So if you’re trying edibles, go slow and be patient. Give it time before you go crazy shoving those weed brownies into your face.
Most experienced cannabis consumers have, at one point or another, gotten themselves to a place they didn’t want to be. You didn’t check the dosage on that edible, and now you’re regretting it. You’re uncomfortable. You may be feeling downright miserable. It’s okay. You’re not going to die. It will pass. Lesson learned.