After a comprehensive review of the scientific literature, researchers have discovered a whopping 13 (thirteen) deaths caused by cannabis. We describe the following:
About 190 million people worldwide use marijuana recreationally. In addition, an estimated 20% of the world population has ever used marijuana.
When people smoke marijuana, THC concentrations quickly rise in the blood, but consequently disappear just as fast. Within one hour, the concentration of THC in the blood is less than 10% of the peak concentration, and after a few hours there are only small amounts detectable. As such, any effect of smoked cannabis should appear fast and disappear also fast.
Oral cannabis consumption (e.g. brownies or cookies) leads to much lower levels of THC in the blood, but considerable amounts of 11-hydroxy-THC forms during metabolism. This metabolite has a similar effect to THC and is responsible for the effects of the oral use of cannabis.
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Some heavy cannabis uses might develop psychoses, while others might have worsened psychomotor skills and cognitive performance. The use of synthetic cannabinoids has also resulted in a number of emergency room visits linked to cardiovascular problems and some users have even died.
Given the potential danger caused by synthetic cannabinoids, the question arises: how dangerous is cannabis? Cannabis so far has been considered relatively safe, and its medical use has also been on the rise. Therefore, it is important to assess its safety, especially deaths caused by cannabis.
O.H. Drummer and colleagues performed a search in PubMed and Scopus (the two largest medical databases) and looked at scientific publications that described deadly events attributable to cannabis (but not to synthetic cannabinoids).
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The authors found altogether 31 case reports that described hospital emergency department admissions linked to cannabis use. While the case reports do not contain much information about prior cannabis use, they all describe some kind of cardiovascular episode.
Even though not all patients underwent drug testing to confirm marijuana use, but those who did, tested positive for THC.
The most common symptoms were chest pain along with arrhythmia, acute myocardial infarction, angina, and minor strokes. Altogether 24 patients had no evidence of coronary artery disease. Instead, they experienced vasospasm and/or arrhythmia.
The authors found six case reports describing 13 individuals where death was linked to recent use of cannabis. These people were aged between 17 to 52 years, all male, and they apparently died after consuming marijuana.
However, five cases had some minor underlying pathology that apparently the consumption of marijuana exacerbated. As such, the authors concluded that marijuana was a major contributor to their death by worsening the underlying medical conditions of these patients.
One person died due to an acute ischemic event with no obvious prior medical condition.
While all except one of these dead people tested positive for THC either in a blood test or in a urine test, the one that tested negative for THC had evidence of marijuana smoking. None of these people had consumed any other drugs, only marijuana.
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Epidemiological studies assessing a possible link between cannabis use and cardiovascular diseases indicated an increased mortality risk or associations with cardiovascular risk.
What these studies found was that the risk of myocardial infarction was almost 5 times as high an hour after marijuana smoking than before smoking. However, this risk was only 70% higher two hours after smoking.
Several epidemiological studies (including a large study of 2 million hospitalized patients) revealed no increased risk of death due to marijuana smoking. The did, however, detect an increase in respiratory failure, cerebrovascular disease, septicemia, and dysrhythmia.
The consumption of THC increases heart rate and cardiac output, especially in new users who are not yet used to the effects of marijuana consumption. This effect is probably due to the activation of the CB1 receptor.
The are some issues that complicate the assessment of death caused by cannabis. First, illegal marijuana types contain more THC and little to no CBD, and therefore can be riskier than medical marijuana types. In addition, since THC might be undetectable after a prolonged time, deaths that are attributable to cannabis might go unidentified because THC is not detected in these cases.
All in all, death by cannabis use is a rare even although a potential possibility. Indeed, large-scale epidemiological studies failed to find any evidence of increased mortality and cannabis use. Case studies, however, show that the effects of THC are more pronounced and therefore potentially deadly in novice cannabis users, and in people with preexisting medical conditions.
Drummer OH, Gerostamoulos D, Woodford NW. Cannabis as a cause of death: A review. Forensic Sci Int. 2019 May;298:298-306.