A new study documents a sharp rise in emergency-room visits linked with marijuana following legalization in Colorado.

A key driver of the ER trips appears to be edibles like weed brownies and cookies.

Despite their meager sales, edibles represented a far higher proportion of weed-related ER visits compared against those for smoked marijuana.

Looking for a uniquely risky way to consume marijuana? Try an edible.

That's the take-home message of a new study of weed-related emergency-room visits following legalization of the drug in Colorado.

For their paper, published on Monday in the journal Annals of Internal Medicine, a team of clinicians reviewed more than 2,500 cannabis-related emergency visits to a large public hospital in the state between 2012 and 2016.

Cannabis was legalized medically in Colorado in 2009 and recreationally in 2014.

While the hospital saw about 200 cannabis-linked ER trips in 2012, that figure jumped to roughly 800 in 2016, the authors of the study found. The uptick was chiefly driven by smoked marijuana, where people who experienced troubling symptoms like severe nausea and vomiting tended to show up in the emergency department after chronic or heavy use.

Edibles were another big problem.

Pot brownies, cookies, and other sources of cannabis that are ingested can confuse patients and lead to issues like paranoia and intoxication. Those problems are especially true for people who are new to marijuana, Andrew Monte, the new paper's lead author and an associate professor of emergency medicine at ​​​UCHealth University of Colorado Hospital, told Business Insider.

"I don't think people are educated enough about how much cannabis to take and how long to wait," Monte said.

For their work, Monte and his team chronicled nearly 10,000 emergency-room visits to the University of Colorado Health's Anschutz campus in Aurora, a large public hospital 30 minutes from Denver. Of all the visits, roughly a quarter, or about 2,500, were linked with marijuana. Of those more than 10% were tied with edibles.

Monte called the finding "striking," especially in light of how few cannabis edibles are sold in Colorado compared to cannabis flower, a term for the kind of marijuana that is smoked.

Not all edibles are created equal

Pot brownies, cookies, and other edible sources of cannabis can confuse patients and lead to issues like paranoia and intoxication. Melia Robinson/Business Insider

Compared against emergency-room visits for smoked marijuana, the proportion of visits for edibles was "about 33 times higher than expected," Monte and his team wrote in their paper.

Monte has several ideas about why it might be happening.

New and inexperienced marijuana users may be more likely to try edibles, for example, because they perceive them to be safer or less intense. But compared with inhaled marijuana, whose effects emerge within minutes and last for three to four hours, ingested cannabis can take hours to have an effect. But those effects can also last for up to 12 hours — putting the trip length on par with that typically seen for the psychedelic LSD.

"With inhaled cannabis, people feel high right away and generally know when to stop. If people have eaten something and don’t feel it, they tend to try more, and that makes things difficult," Monte said.

In addition, there can be wide discrepancies in edible products' actual cannabis content.

Part of the problem is the lack of standards around dosing and labeling with edibles. A 2014 analysis by the Denver Post revealed that out of dozens products labeled with 100 milligrams of THC, some contained virtually zero milligrams of the ingredient while others contained nearly 150 milligrams.

"Can you imagine accepting that kind of inconsistency for any other product?" Monte said. "That's not something we'd accept for any other food or medication that I can think of."

Still, Monte emphasized that weed-related emergency visits are not overwhelming his hospital. In fact, he said he was fairly accustomed to seeing a spike in ER visits when a new drug is introduced into a community. Based on the figures in his paper, if his team is seeing 300 ER patients every day, only one of those visits is related to marijuana, he said.

"The thing to remember here is that cannabis isn't killing everyone, but it's not curing everything either," Monte said.