A relatively higher frequency of visits to an emergency room (ER) in Colorado as a result of ingesting cannabis edibles alludes to the fact that this mode of consumption poses a potential threat that other modes don’t.
The phenomenon was examined by a study published earlier this year in the Annals of Internal Medicine, which investigated ER visits in a single, urban hospital in Colorado between January 2012 and December 2016.  By examining ER charts from that timeframe, the study found, based on patient self-reports, that edibles were responsible for 9.3% of cannabis-attributable visits. Worryingly, while accounting for almost a tenth of ER visits coded as cannabis-related, edibles constituted only 0.32% (by weight of THC) of all cannabis sales in the state between 2014 and 2016. These findings suggest a discrepancy between people’s reaction to edibles versus inhaled forms of cannabis consumption.
While the lay media has mostly attributed this discrepancy to the much longer time it takes for the effects of edibles to kick in, making it hard for people to gauge their state and consume with caution, this is likely only part of the story.
The likelier reason behind these edible-related ER visits is the actual nature of the high induced by edibles, which can go beyond typical cannabis effects and often border with the distorted state of mind we associate with psychedelics. This is because of the different way ingested THC is encountered by the body—or more precisely, the part of the body it is first encountered by.
When we ingest edibles, a much higher portion of the THC consumed is metabolized before going to the brain when compared to inhaled consumption, because all blood flow from the gastrointestinal tract must first flow through the liver before going on to the heart. The liver’s first-pass metabolism converts THC into 11-hydroxy-THC (11-OH-Δ⁹-THC), a vastly different cannabinoid that has barely been studied. But from the little we do know about it, it seems much more potent and unpredictable than THC itself.
The main study we can refer to on this matter dates back to 1973, in which nine men were first given 11-hydroxy-THC, and then THC, and were asked to compare their experiences. 
“After the intravenous administration of 11-OH-Δ⁹-THC, there were pronounced psychologic and pharmacologic effects…A marked tachycardia, an intense psychologic high, and considerable symptoms were produced,” wrote the researchers from the Lilly Laboratory for Clinical Research. “All subjects reported a maximum psychologic high within 2-3 min after the intravenous administration of 11-OH-Δ⁹-THC that was more intense than that previously experienced after smoking [cannabis].” Supporting these previous findings, results from the Colorado ER study showed that the chief complaint in cases of edible ingestion was more likely to involve acute psychiatric symptoms, intoxication, or cardiovascular symptoms compared to other types of cannabis consumption. 
Additionally, the liver also binds 11-OH-Δ⁹-THC to glucuronide compounds, which are water-soluble and act like raft boats that carry 11-OH-Δ⁹-THC through our bloodstream and across the blood-brain barrier. So even though orally-consumed cannabinoids take longer to flow into our brain and affect our mind, once they do, it’s not a gradual stream that breaks through but a proper flood.
While the data presented indicates a correlation between edible cannabis consumption and increased ER visits, there are several important caveats. First, the time period during which the study was conducted represented a period shortly following adult-use legalization in Colorado, when issues related to proper dosing of edibles were shown to be problematic across state lines.  Second, the study draws on ER data from a single facility in a single state, making generalizations presumptuous. Third, all information concerning the method of cannabis consumption is patient self-reported.
So, the bottom line is, before we label edibles as dangerous and/or of poor quality, it’s important to appreciate the science behind their sometimes-overwhelming effects. Such knowledge can instill patience and caution, through which we can possibly tame and even harness this different kind of experience.
- Monte et al, “Acute Illness Associated with Cannabis Use, by Route of Exposure: An Observational Study”, Ann Intern Med. 2019;170(8):531-537. [Journal Impact Factor = 19.315; Times Cited = 10]
- Lemberger et al, “Comparative pharmacology of Delta9-tetrahydrocannabinol and its metabolite, 11-OH-Delta-9-tetrahydrocannabinol”, J Clin Invest.1973 Oct;52(10):2411-7. [Journal Impact Factor = 12.282; Times Cited = 73]
- Vandrey, R. et al, “Cannabinoid Dose and Label Accuracy in Edible Medical Cannabis Products”, JAMA. 2015;313(24):2491-3. [Journal Impact Factor = 51.273; Times Cited = 156]
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