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According to the National Safety Council, in 2021 in the US, 1159 people died of cannabis overdose, of which 1130 of the deaths were preventable:

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Is this true?

I'm skeptical because the drug enforcement agency says on its Marijuana/Cannabis Factsheet "No deaths from overdose of marijuana have been reported".

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  • 40
    I'm also very curious about the 29 unpreventable cannabis deaths due to overdose.
    – Ben Hocking
    Mar 8 at 13:22
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    I did find this single example as to a THC-delivery device that can lead to overdose (cannabis contains THC), but it doesn't answer your question: newsweek.com/…
    – Ben Hocking
    Mar 8 at 13:25
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    Also, the CDC page on overdoses has a section on marijuana, and while it mentions negative effects, it doesn't actually mention overdoses, despite that being the primary subject matter of the page: cdc.gov/drugoverdose/deaths/other-drugs.html#marijuana
    – Ben Hocking
    Mar 8 at 13:28
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    The chart says "select drugs". I wonder why they chose to select cannabis and not nicotine and alcohol. Alcohol Poisoning Deaths — CDC says that over 2000 people per year die of alcohol overdoses, and that's a direct cause, not simply contributing.
    – Ray Butterworth
    Mar 8 at 19:24
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    @RayButterworth Contributing would clearly shoot that number sky high. DUI incidents are non-trivial, and there are a lot more other types of contributing deaths and injuries.
    – Nelson
    Mar 9 at 2:15

2 Answers 2

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That's not what this data says.

What's happening is that in cases of overdose deaths, both causative and contributing drugs get listed in this report. We have a hint in the description of the data, which states, "When comparing deaths by drug type, multiple drugs are often listed for one death." According to the data table, statistics are generated using ICD codes:

Deaths are classified using the International Classification of Diseases, 10th Revision. Preventable drug poisoning deaths are identified using underlying cause-of-death codes X40-X44, while all drug poisoning deaths are identified by codes X40-X44, X60-X64, X85, and Y10-Y14.

Among deaths with drug overdose as the underlying cause, the following multiple cause-of-death codes indicate the drug type(s) involved: Any opioid (T4NR-T40.4, T40.6), heroin (T40.1), methadone (T40.3), synthetic opioids other than methadone (including fentanyl, T40.4), natural and semisynthetic opioids (including oxycodone and hydrocodone, T40.2), benzodiazepines (T42.4), cocaine (T40.5), and cannabis (T40.7). Deaths involving more than one opioid category are counted in both categories.

Digging into the ICD codes a little deeper, however, we find this information, emphasis mine:

Codes for underlying cause of overdose death include the letter X or Y (for example, X40: accidental poisoning, X60: intentional self-harm).

Codes for opioid-related contributing cause of overdose death include a T (for example., T40.1: heroin, T40.4: other synthetic opioids).

https://mnprc.org/wp-content/uploads/2019/01/using-icd-10-codes-to-assess-opioid-related-overdose-deaths.pdf

So, cannabis is only uniquely identifiable in this dataset under code T40.7, which merely indicates a "contributing cause" but not an "underlying cause" of death. I can't find any ICD code that denotes cannabis as an underlying cause of death - one might infer from the lack of such a code that fatal cannabis overdose is exceedingly rare.

Overall, it seems this data indicates that there were 1,130 people that died from a drug overdose who had marijuana listed as a contributing - but not principally causative - factor in the death. The data does not indicate that there were 1,130 deaths whose underlying cause was cannabis overdose.

It is possible that there are deaths caused by cannabis overdose which appear in other categories, but from this data there is no way to ascribe a number specifically to cannabis. It's theoretically possible that over 1000 fatal cannabis overdoses appear in other categories, but it seems medically unlikely. While we can't conclude from this data that there aren't over 1000 fatal cannabis overdoses, we also can't conclude from this data that there's even 1 fatal overdose caused by cannabis.

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    @DavePhD That's not so ridiculous if you think about drugs which lead to strong physical dependence - during withdrawal, improper care could lead to death from complications of vomiting and diarrhoea, for instance. As far as I know, cannabis generally doesn't cause physical dependence of that sort, so "lack of cannabis" is unlikely to be even a "contributing cause".
    – IMSoP
    Mar 8 at 17:29
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    And it also doesn't distinguish between cannabis ONLY and cannabis "found in system". If someone died of a multi-drug OD, cannabis will end up part of the "contributing" even though someone ODing and die from it alone is almost unheard of.
    – Nelson
    Mar 9 at 2:18
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    Note that the non-existence of an ICD-Code meaning 'underlying cause of death is a cannabis overdose' implies that the WHO, who administers these codes currently believes this is not even potentially a valid diagnosis. The list of existing ICD-Codes gets updated every year and if the WHO believed there could be cases where such a code would be appropriate, then it would exist.
    – quarague
    Mar 9 at 7:34
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    @NeilMeyer I specifically said "physical dependence of that sort" - i.e. the sort of dependence that produces potentially dangerous withdrawal symptoms such as vomiting and diarrhoea, so I'm not sure how "a sedation effect that can be habit forming" is relevant.
    – IMSoP
    Mar 9 at 16:37
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    @NeilMeyer that's utter nonsense. Not even the same planet as those two. Withdrawal from long term use of benzos requires significant medical intervention and careful tapering, possibly even the use of other medications. Meanwhile Snoop Dogg could quit tomorrow and while it would be unpleasant, there would be no other medical issues. Benzos are also vastly more addictive for most people, with physical dependency possible in literal weeks time
    – eps
    Mar 9 at 19:32
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If you "Download Table" from https://injuryfacts.nsc.org/home-and-community/safety-topics/drugoverdoses/data-details/ there's a bit more detail on where these data came from:

Deaths are classified using the International Classification of Diseases, 10th Revision. Preventable drug poisoning deaths are identified using underlying cause-of-death codes X40-X44, while all drug poisoning deaths are identified by codes X40-X44, X60-X64, X85, and Y10-Y14.

X40-44 are all "accidental poisoning" causes, each number is a different category of drug. X60-64 are "intentional self-poisoning" equivalents. X85 is "assault by drug", Y10-Y14 are the "undetermined intent" equivalent of X40-44/X60-64. See https://mnprc.org/wp-content/uploads/2019/01/using-icd-10-codes-to-assess-opioid-related-overdose-deaths.pdf

None of these codes identify cannabis specifically. That is, while you could categorize a cannabis overdose under one of these codes, you would not be able to identify it as a cannabis overdose from the code. For example, X62 includes cannabis but also cocaine and heroin. The only way you'd specifically identify a cannabis overdose from these ICD codes is from the T40 range:

Among deaths with drug overdose as the underlying cause, the following multiple cause-of-death codes indicate the drug type(s) involved: Any opioid (T4NR-T40.4, T40.6), heroin (T40.1), methadone (T40.3), synthetic opioids other than methadone (including fentanyl, T40.4), natural and semisynthetic opioids (including oxycodone and hydrocodone, T40.2), benzodiazepines (T42.4), cocaine (T40.5), and cannabis (T40.7). Deaths involving more than one opioid category are counted in both categories.

It seems likely that any time T40.7 is present, some other code is also present that indicates the "actual" cause of death.

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  • Is the raw data available that would allow us to go from "likely" to "definitely" on your conclusion?
    – IMSoP
    Mar 8 at 16:27
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    @IMSoP Possibly but I didn't see an explicit reference in the source to their source data. What is definitive is that it is not possible to ascribe a single cause using these codes.
    – Bryan Krause
    Mar 8 at 16:53
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    I'm curious what subset of those numbers include (X62|X42|Y12)+T40.7... that might be as close as we can get to "cannabis may have been a significant factor in or potential underlying cause of death"
    – Doktor J
    Mar 8 at 21:04
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    @DoktorJ The T-codes are not mutually exclusive, So one would have to look for some X/Y code for death by drug overdose + T40.7 + no other T4xxx code to get cases where cannabis is the most significant factor.
    – quarague
    Mar 9 at 7:40
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    @TimSparkles I changed "mentions" to "identifies". I provide an example in the next sentence of what is meant by this. None of these codes are for cannabis specifically, so you cannot use them to identify cannabis overdose.
    – Bryan Krause
    Mar 14 at 22:08

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