A lot of visitors to Colorado figure they might give the state's good ganja a try. But they might not be prepared for the effects. When it comes to bad weed trips, out-of-staters have been doing much worse than Colorado residents and are going to the ER more often since recreational sales of marijuana began in 2014.

The number of out-of-state residents who ended up in the emergency room for cannabis-related reasons nearly doubled from 2012 to 2014, according to an analysis of emergency department visits in 100 Colorado hospitals. By contrast, the number of Colorado residents visiting emergency rooms for cannabis increased about 40 percent in those two years, according to the studypublished in the New England Journal of Medicine on Wednesday.

There are marijuana-specific tours, like those run by My 420 Tours, but many of these visitors seem to be in Colorado for other reasons, says lead author Dr. Howard Kim, an emergency medicine physician and a postdoc at Northwestern University. "I remember some business travelers who were in Denver on business, and after the meeting ended, they decided to try some marijuana edibles. Then they ended up cutting to the ER."

Kim was finishing his residency in Colorado when he did the study. A lot of the people ending up in the ER where Kim was finishing his residency had classic signs of marijuana intoxication. "People can be anxious or agitated or even have brief psychotic episodes like hallucinations and delusions," he says. "Patients can have a very fast heart rate or gastrointestinal problems like vomiting."

It's not clear why Colorado residents are doing better than the visitors, but Kim thinks it probably has to do with better understanding of marijuana and its side effects. "Right now, I think it's just an awareness gap." he says. "The Colorado Department of Public Health and Environment has done a great job. But it's not as easy to educate the entire population of potential visitors to Colorado."

Adam Curtis, who owns a cannabis dispensary called The Giving Tree of Denver, says "All my employees have a copy of the Good To Know," These are pamphlets and notecards that the Colorado Department of Health and Environment distributes to marijuana retailers as part of a state public health education campaign.

He thinks that sellers have been doing a good job of educating the customers, and the three retailers, including The Giving Tree if Denver, Shots contacted all said they provide literature from the department of health including the Good To Know materials.

Curtis advises first-time recreational users to take half the 10 milligram recommend dosage of THC. He speculates that people ending up in the ER are going above that dosage against the recommendations on packaging or by marijuana sellers.

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