Should You Worry about a Fatal Cannabis Overdose?

Published on June 12, 2019

The CDC webpage poses in its FAQ: “Is it possible to ‘overdose’ or have a ‘bad reaction’ to marijuana?”

To answer, they say, “A fatal overdose is unlikely.” Of course, since there is not a single overdose death from cannabis in recorded history, they could have said that. Maybe that’s what they meant by “unlikely.”

“Ah,” you say. “But, I just heard about a fatal marijuana overdose in Louisiana.”

Some facts of the case

How did the coroner in the case, Christy Montegut, decide that the cause of death was cannabis intoxication? A woman died at home on her couch.  There were no other drugs in her blood, and all the organs looked healthy. Christy reported that the postmortem THC level was 8.4 nanograms per milliliter of blood. To show up on his toxicology report, the THC level needed to be at least .5ng/mL.  In comparison the per se level of intoxication for THC that some states have written into law is 5 ng/mL. Coroner Christy drew his conclusion of cannabis overdose because the 8.4 ng/mL result was 15 times higher than the .5 ng/mL level.

Blood tests for cannabis

I have written before about the lack of a scientific basis for per se laws, setting a legal limit for blood THC levels. As I said there, THC blood levels do not predict impairment. Because THC accumulates in fat tissues, THC blood levels can stay elevated for days or weeks in frequent cannabis consumers.  

As a comparison, researchers have found a blood THC level of 8.2 ng/mL can cause driving impairment (not death). This is seen in people who have a breath alcohol concentration of 5 percent—the level at which driving impairment appears. Bernard Le Foll, a professor and scientist at the University of Toronto who studies addiction reported that there is no agreed upon threshold where cannabis could be fatal, and a possible fatal level would need to be between 100 and 1000 thousand times the level in the Louisiana death.

THC blood levels postmortem

It turns out that measuring THC from a dead person is even more inaccurate than analyzing the blood of someone alive.  Andrea Tully’s dissertation found that THC levels in blood increase the longer a person has been dead.  This is postmortem drug redistribution.  After death, highly lipophilic drugs will be released from organs like the liver into the blood stream, producing THC levels at autopsy are significantly higher than at the time of death.

And Coroner Christy has an even bigger problem defending his ruling of the cause of death. It turns out that THC blood levels vary when you draw the blood from different places in the body.  When drawn from different parts of the body, Tully found that blood THC levels varied in one person from 2.1 ng/mL to 6.6 ng/mL, and another person’s THC ranged from 2.9 ng/mL to 40.9 ng/mL.

Some fatality comparisons

Opponents of ending prohibition of cannabis may try to make a big deal of this “overdose” death.  Of course, even a single overdose death is tragic. In comparison, NIDA reports over 70,000 drug overdose deaths from 1999-2017, none from cannabis.  That’s about 3,600 per year. The CDC reports a yearly average of acute alcohol-related deaths of over 49,000 per year. In comparison, the National Institute of Drug Abuse acknowledges that, “There are no reports of teens or adults dying from marijuana alone.”

In conclusion, did you know that coroners do not have to have any medical training at all? To be a coroner in Louisiana, you need to be 18 and have a GED or high school diploma.  Coroner Christy, after doing his “research” on the internet, decided that vaping a concentrated cannabis oil caused the death. 

Michael Milburn is Founder and Chief Scientific Officer for DRUIDapp, Inc.  The DRUID® app calculates the level of impairment from cannabis or any other source in 2 minutes by measuring reaction time, decision making, hand-eye coordination, balance and time estimation.  He has just been awarded a substantial Small Business Research Grant from NIH for research on DRUID.  Dr. Milburn holds degrees from Stanford (AB) and Harvard (PhD), and he was Professor of Psychology at the University of Massachusetts/Boston for 40 years, with a specialty in research methods, measurement and statistics.  His unique set of skills enabled him to develop the DRUID® impairment measurement app, now in the App Store and Google Play.

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