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Pot brownies and other cannabis “edibles” like gummy bears that are sold online and where marijuana is legal may seem like harmless fun, but new research indicates that edibles may be more potent and potentially more dangerous than pot that is smoked or vaped.

The new study analyzed thousands of cannabis-triggered emergency room visits in the greater Denver area, and found that edibles induced a disproportionate number of pot-related medical crises. Edibles were also more likely than inhaled pot to cause severe intoxication, acute psychiatric symptoms in people with no history of psychiatric illness and cardiovascular problems.

Pot smokers, on the other hand, were more likely to have gastrointestinal complaints, including a vomiting condition called cannabinoid hyperemesis syndrome, and they were more likely to be hospitalized if they needed emergency care.


Emergency room doctors in Colorado started noticing several years ago that “there were a lot of visits associated with edibles, even though they were not the predominant product used, and they seemed to be sicker compared to those who inhaled,” said Dr. Andrew Monte, an associate professor of medicine and the lead author of the new study, published in Annals of Internal Medicine on Monday.

He also noted that the only deaths in Colorado that have been definitively attributed to cannabis involved edibles, and those deaths were surprisingly violent. In all three incidents, including a murder and a suicide in 2014 and another suicide in 2015, the pot users exhibited extremely erratic behavior after consuming edibles, according to news reports and trial testimony.

Ingested pot takes longer to produce a high than smoked pot, making it harder to gauge the right dose to achieve the desired effect, which increases the risk of an overdose, experts say. Ingested pot also takes longer for the body to clear.

“When you’re smoking marijuana, you start seeing the effects in a couple of minutes,” said Dr. Nora D. Volkow, director of the National Institute on Drug Abuse at the National Institutes of Health, who wrote an editorial accompanying the study. “But when you take it orally, it takes a long time to feel the effects, and if you’re taking it in order to feel good and you feel nothing, you may think you didn’t take enough. This is a common phenomenon. People take another dose.”


The edible candies “look very innocent and safe, so you take another and another, and slowly it is being absorbed. And then you start to feel awful, before you complete the absorption, and that can lead to a psychotic episode,” Volkow said.

Responses to the effects of edibles and the rate of absorption vary from one person to another, and the THC content in products may not be labeled accurately, she noted. Absorption of edibles will also vary depending on the fat content of the food one has consumed, she said, noting that “the content in your blood is going to be much, much higher when you take it with chocolate or a brownie rather than a gummy bear.”

The new study found that though edibles represented less than one-third of 1 percent of the state’s total cannabis sales by weight of THC between 2014 and 2016, they accounted for 238 of the 2,432 cannabis-triggered visits to the UCHealth University of Colorado Hospital Emergency Department, or about 10 percent. The authors calculated that there was 309 times more THC sold in flower or smoked form compared with edible products during the three-year period examined.


Symptoms also tended to vary depending on whether the pot was consumed as an edible or smoked. Nearly half the emergency room patients who had consumed edibles complained of intoxication or altered mental status, often accompanied by anxiety, compared with less than a third of those who had smoked the pot.

About a quarter of both the smokers and those who consumed edibles experienced psychiatric problems, but those who used edibles were more likely to exhibit acute psychiatric symptoms, while the smokers were more likely to complain of an exacerbation of a chronic condition like depression.

In addition, 8 percent of edible users had cardiovascular symptoms, including rapid or irregular heart rate, compared with only 3 percent of pot smokers. Serious cardiovascular events, including heart attacks, occurred in both groups. Other studies have also reported on the emerging concern of cardiovascular problems being associated with pot use, Volkow said.

Concerns about edibles are not new, and many states that have legalized recreational or medical cannabis, including Colorado, California, Rhode Island, Nevada and Oregon, require packaged edibles to carry a warning that the intoxicating effects may not be felt immediately, said Camille Gourdet, a researcher who studies state cannabis policies at RTI International, a nonprofit research organization.

Many states also require edibles to be clearly marked with a symbol warning consumers that the products contain cannabis and are not regular food items, Gourdet said. Several states also require edibles to have even distribution of THC content throughout the product so it is not all concentrated in a single bite of a cookie or brownie.


Monte, who sits on the Colorado Retail Marijuana Public Health Advisory Committee, said he does not think edibles should be available in the retail recreational market. He said the important message for consumers is that there are more adverse drug events associated with edibles than with inhaled products, and that edibles are more likely to trigger psychiatric illness. First-time users — a group that, in Colorado, often includes tourists, are at particular risk, he said.

“If they’re going to take an edible, they should use a very low dose, 5 or 10 milligrams,” he said. “Take it and do not re-dose before four hours, because it may take a while.”

Last week, the state medical societies of New York, New Jersey, Connecticut and Delaware put out a joint statement saying that while they support changing the legal status of the drug to facilitate research, they oppose the legalization of recreational marijuana because there is not enough research proving that marijuana is safe.

“We must look at the potential effect legalization will have on overall use and significant harms, including impaired driving and accidents, creation and worsening of severe mental health issues, and negative impacts on developing minds,” the statement said. “States that are rushing toward legalization of recreational marijuana are ignoring how profit-driven corporations hooked generations of Americans on cigarettes and opioids, killing millions and straining public resources.”