Colorado visitors using marijuana more likely to end up in emergency room

"Emergency room visits related to cannabis use have increased more dramatically among out-of-state visitors than among Colorado residents," said lead investigator Dr. Howard Kim, a postdoctoral fellow in emergency medicine at Northwestern University Feinberg School of Medicine and an emergency medicine physician at Northwestern Medicine. "This may indicate that out-of-state visitors are unprepared for the adverse effects of marijuana use."

Kim began the study when he was a resident at the University of Colorado School of Medicine.

The finding has implications for other states in which recreational marijuana is legal, such as Alaska, Oregon and Washington.

The study will be published in the New England Journal of Medicine print issue on February 25, 2016.

Adverse effects of marijuana use may include psychiatric symptoms such as anxiety, hallucinations and altered mental status; cardiovascular symptoms such as a fast heart rate, high blood pressure or palpitations; and gastrointestinal symptoms including abdominal pain and vomiting.

Although the investigators did not study if visitors to the emergency room used primarily edible or smoked cannabis products, edible products such as cookies or brownies often have a delayed effect, which could lead to overdosing, Kim said.

"People eating marijuana products often don't feel any effect immediately, leading them to eat another edible," Kim said. "Then they've ingested multiple products, so when the effect finally kicks in, it is much stronger."

In addition, the content of edible products is highly variable, so users don't know the potency of what they are eating.

Out-of-state visitors to the emergency room for marijuana-related symptoms accounted for 78 per 10,000 emergency room visits in 2012 compared to 163 per 10,000 visits in 2014 -- an increase of 109 percent. Among Colorado residents, the number of marijuana-related visits was 70 per 10,000 in 2012 compared to 101 per 10,000 in 2014, a 44 percent increase. The research took place in the emergency department of UCHealth's University of Colorado Hospital.

"Anecdotally, we noticed that most out-of-towners were in Colorado for other reasons, such as visiting friends or on business," Kim said. "They ended up in the ER because they decided to try some marijuana." Most patients got supportive care and went home after a few hours, but some were admitted for further observation.

"Everyone needs to be aware of the side effects of marijuana use," said senior author Dr. Andrew Monte, assistant professor of emergency medicine at the University of Colorado School of Medicine. "These results underscore the importance of educating the public and especially any visitors to marijuana-legal states on safe and appropriate use of cannabis products."

Monte said the Colorado Department of Public Health and Environment's "Good to Know" campaign has improved education of users across the state, reflected in lower rates of emergency department visits among Colorado residents.

In addition, new regulations in Colorado require training on responsible use for budtenders, as cannabis dispensary workers are known. These efforts aim to decrease adverse effects for all users, including those with less knowledge and experience.

Kim and Monte recommend that any states considering liberalizing marijuana policies should implement pre-emptive public health education campaigns.