Doctors say chronic marijuana use may be linked to an illness known as CHS, or Cannabinoid Hyperemesis Syndrome. In recent years, the number of known cases doubled in Colorado.

Experts say CHS is caused by chronic or heavy use of marijuana, which means ingesting or smoking marijuana at least once a day.

The symptoms can be severe. Patients have reported intense, non-stop nausea and stomach pain that can sometimes last up to a month.

Dr. Kennon Heard, a physician with the University of Colorado Hospital, is one of several doctors studying the effects of CHS.

He and his team found that the number of hospital visits for CHS doubled since medical marijuana became prevalent. The study takes a closer look at more than 2,500 hospital visits. From 2008 to 2009, the study found there were 41 visits to emergency rooms for CHS. From 2010 to 2011, after what the study describes as the “post-liberalization” period for medical marijuana, the number jumped to 87 ER visits.

"We see them here on a daily to weekly basis," Dr. Heard said.

Dr. Heard says CHS is not a major health problem if you compare it side by side to the consequences of alcohol use. However, he adds that symptoms can be severe and can last for months.

"You can imagine ending up in the emergency department 3 to 5 times," Dr. Heard said.

Experts say, the number of people suffering from CHS is unclear because not everyone who has it goes to the hospital.

"The biggest problem we've seen with this disease is that until now, it's been unrecognized and therefore, these people are suffering longer than they need to."

Many marijuana users have asked why they are only now hearing about CHS. Dr. Heard says, while the illness may have been documented as early as 2004, the symptoms haven't always been recognized.

"If you asked me 10 years ago, I would say it didn't really exist," Dr. Heard said.

Dr. Heard says CHS is in many ways still a mystery. He still doesn't know the reason marijuana triggers symptoms like nausea and stomach pain. Only that there definitely seems to be a link.

"Nobody actually knows the reason this happens," Dr. Heard said. "This certainly is an area that needs more study."

Experts also say the number of people suffering from CHS can be hard to track because not everyone who has it visits the hospital.

People who have the illness have found ways to relieve the symptoms by taking hot showers and relaxing.

Peter Williams says he's experienced symptoms of CHS for at least four years. He's not sure what triggered the symptoms that sent him to the hospital numerous times.

"I got really sick and it was the most intense nausea I've ever felt in my life that had no relief," Williams said. "The only relief for me was taking scalding hot baths or showers to feel better for 15 minutes."

Williams said he stopped consuming marijuana but once he started again, the symptoms came back.

"I quit marijuana for two months and then I got sick again and I thought, it can't be the marijuana. But I don't think two months was long enough to get it out of my system," Williams said.

Williams, who just recovered from CHS, said he'll wait at least six months before trying to smoke again. He wants pot users to be cautious but not afraid of consuming marijuana.

"I see the benefits of marijuana everyday," Williams says.

Doctors say, people experiencing symptoms should visit a doctor immediately, adding that CHS can lead to dehydration and kidney problems if it goes unchecked.

Dr. Heard says the cure to CHS is simple: stop using marijuana. Patients in the hospital are also sometimes given medication to help with the nausea or stomach pains.

You can find a link to Dr. Heard's study here: