Smoking marijuana during the 2014 4/20 marijuana festival, in Denver's downtown Civic Center Park. 

(AP Photo/File)

As more states legalize medical and recreational marijuana, emergency room physicians in Colorado warn their colleagues around the country to be on the lookout for an illness that strikes heavy users of marijuana. It’s called cannabinoid hyperemesis syndrome -- a nasty affliction whose central symptom is uncontrollable retching and vomiting. There are a lot of unanswered questions about it because cannabis research has been thwarted for so long. But Dr. Kennon Heard, a toxicologist at the University of Colorado School of Medicine, says it’s a real problem that goes beyond pot tourists overindulging. Heard co-wrote a peer-reviewed paper on the condition in the journal "Academic Emergency Medicine."

Related:

Interview Highlights With Dr. Kennon Heard

What it feels like to have cannabinoid hyperemesis:

"It will cause a lot of abdominal pain nausea, vomiting. Patients are really, really uncomfortable. It’s a sort of uncontrollable dry retching and abdominal pain and they feel terrible. ...It can last for several days. It's a recurrent disease so patients can get it, get a little better for a few days, then it can come back and they can even have multiple episodes of this of the course of several months."

How often he sees it in the emergency room:

"Really, a daily to weekly basis. And talking to my colleagues around the state, you know it's pretty much everyone is seeing it to some extent."

What kind of person is most likely to get it:

"We don't have a really good characterization of this yet. There hasn't been a lot of systematic evaluation. I can tell you in our emergency department the majority of people that we see are really consistent with the people who are most commonly using marijuana. So: younger, a little bit higher proportion of males, people who are using or report heavy use -- usually daily at least."

Does this happen through smoking and the use of edibles?

"The vast majority the patients that we're seeing in our emergency departments are smoking. I don't think we have really good information about how often it occurs with each type of exposure but my impression is that it's more common with smoking than with edibles."

Why this illness strikes:

"Based on the fact that it's usually seen in people are a frequent heavy users, what we see with other drugs is frequently the nervous system changes in response to that constant stimulation from the from active chemicals in the drug, something like you'd see from someone who becomes dependent on opioids or alcohol for example, and as you are exposed to the drug or heavy amounts of the drug for a long period of time, your body makes adaptations to that. And then those of adaptations can likely cause the effects we are seeing. Now we don't have any real good science to explain what exactly those adaptations are; that's very much a 30,000 foot view and we'd like to get some more information because it will help us understand the cause of this disease and potentially even some other therapeutic ways that that cannabinoids could be used."

Why he’s spreading the word now:

"There's been a lot more interest in this with the recent elections and the increased availability of marijuana in other states and we think it's important that people are aware of this kind of disease that can trigger emergency department visits. It really can dramatically affect people's lives. They’re miserable when this happens. It's going to keep him home from work it's going to prevent them from doing the things that they need to do and it also triggers a very extensive evaluation. Patients will get extensive laboratory testing -- X rays, cat scans, all kinds of tests in the emergency department because this can look like a lot of really serious diseases and while this is serious it's not life threatening. If we can let people know that this can occur and they can talk with their doctors, relate their history of marijuana use, it may … prevent some of the extensive work ups and may also suggest a way that these people can, you know, prevent this, which is by cutting back or stopping their marijuana use for at least some period of time."

Why this isn’t “Reefer Madness”:

"I've heard a lot about that and you know, at this point, all I would say is people who are going to use marijuana, that's their choice. In Colorado right now that's their privilege. We want people who are having the symptoms to be aware of this and to at least consider that [a doctor in an ER can say], 'Look we've looked for dangerous causes of your symptoms and the good news is we don't find anything. I think this may be contributing to what you're feeling like this and I ask you to consider whether you want to try cutting back marijuana to see if it helps make you better.'"