This isn't the first time we've seen the negative impacts of marijuana.
A study of use in Colorado published in 2015
found increases in marijuana-related traffic deaths, hospital visits, school suspensions, lab explosions and pet poisonings. In that study, marijuana-related ER visits increased 57% from 2011 to 2013.
This new study from Northwestern Medicine and the University of Colorado School of Medicine reviewed ER visits at more than 100 hospitals from 2012 to 2014. Out-of-state visitor trips to the ER visits for marijuana-related symptoms rose from 78 per 10,000 visits in 2012, to 112 per 10,000 in 2013, to 163 per 10,000 in 2014 -- an increase of 109% from 2012 to 2014.
For Colorado residents, marijuana-related ER visits rose from 70 per 10,000 in 2012 to 101 per 10,000 in 2014 -- a 44% increase.
"Visitors are less-experienced with Colorado cannabis products, which is more potent than what many have previously used," said Dr. Andrew Monte, the senior author of the study and an assistant professor of emergency medicine at the University of Colorado School of Medicine. "People are more likely to use the drug, and use it in excess, when visiting or on vacation."
Authors of the study and public health officials say these results highlight the need for education for consumers that details safe, appropriate use of marijuana products at the places where it's sold.
"It underscores the importance of point-of-sale education at the retail marijuana stores, said Mike Van Dyke, chief of environmental epidemiology at the Colorado Department of Public Health and Environment. "That is the one good thing about this product is that you have designated places where it is sold. I think that is the most targeted point of intervention that you can do. Point-of-sale education is critical."
The findings of this study also have implications for other states where recreational marijuana is legal, such as Alaska, Oregon and Washington, authors said.
"The biggest thing needs to be a public education campaign," 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.
"We really need to do a better job of educating the public about the possible adverse side effects of marijuana use and how to use the product appropriately. If you're going to visit a marijuana-legal state, you should be aware that there can be adverse side effects and you should probably use marijuana products in moderation."
Although researchers did not identify whether ER visitors used edible or smoked marijuana products, edibles such as cookies or brownies often have a delayed effect, said Kim, which could lead to overdosing.
This was the case for a 19-year-old college student who died from jumping off a balcony after eating more than six times the recommended amount of a marijuana cookie. He visited Denver with his friends in March 2014, possibly for marijuana tourism, according to the Centers Disease Control and Prevention
. The autopsy report listed marijuana intoxication as a chief contributing factor.
"Anecdotally, the peak effects for smoking marijuana is typically in five to 10 minutes, while the peak effect for ingesting marijuana is typically two to four hours, said Kim. "Usually inexperienced users may ingest an edible marijuana product and then when they don't feel any effects, eat another marijuana product because they think it's not working. So it's important for inexperienced users to know the effect for ingested marijuana is delayed compared to smoked or inhaled marijuana."
There are three major categories of visits related to marijuana use, Monte said -- related complications, such as motor vehicle collisions or cyclic vomiting; exacerbation of underlying medical conditions, such as anxiety, depression and psychosis; and, in a minority of visits, acute intoxication, which often results in anxiety and a racing heart.
To decrease the adverse effects of marijuana and increase awareness, the Colorado Department of Public Health and Environment established programs such as "Good to Know," which is focused on educating Colorado residents about the side effects of marijuana use, according to Kim. Colorado has also established a responsible vendor program to increase point-of-sale education for consumers.
"I think that people have a different mentality when they go on vacation as compared to when they are home, so it's hard to change behaviors sometimes," said Van Dyke. "It may take a while to see these numbers go down, but we hope these efforts really do reduce these issues that are happening."