Frequent marijuana use appears to be causing a mysterious syndrome characterized by severe nausea and repeated vomiting.

Little is known about the condition, which is called cannabinoid hyperemesis syndrome, or CHS.

Business Insider interviewed half a dozen patients diagnosed with CHS, as well as emergency-room doctors who've treated it and scientists who are studying it.

Patients say the condition has turned their lives upside down. Experts are concerned it may be more common than once believed.

Marijuana is gaining acceptance in the US as more states legalize the drug. But we're just beginning to understand the variety of benefits and risks associated with it.

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Alice Moon once reviewed marijuana edibles for a living. So when a doctor told the 29-year-old Californian that she had to stop using cannabis because of a newly discovered syndrome, it threatened to turn her world upside down.

Before giving up the drug, she wanted one last hurrah. She'd end five years of daily weed use on a high note, she thought.

At a special dinner that evening, Moon ate a five-course cannabis-infused meal prepared by the award-winning chef Holden Jagger. Between dishes, Moon and the other guests were encouraged to take hits of an assortment of joints, hand-selected to complement the flavors in each dish.

Before the meal began, Moon joked with Jagger that it would be her last supper.

A few hours later, she was at home vomiting uncontrollably. She'd spend the next few days in the hospital.

Moon had previously been diagnosed with a condition called cannabinoid hyperemesis syndrome, or CHS.

Very little is known about CHS, which was first identified in the early 2000s. The recognized hallmarks of the condition are heavy, consistent marijuana use, violent vomiting and nausea, and a tendency to use extremely hot baths or showers for relief.

Initially believed to be very rare, CHS has increasingly cropped up in medical journals and emergency rooms (ERs) around the world. There is no known cure. The only long-lasting treatment is quitting cannabis completely.

The condition may be preventable, however, which is one reason doctors and researchers say they want more people to know about it. Research suggests that more adults are using marijuana in recent years; whether that has to do with more states legalizing the plant remains unclear.

Cannabis isn't one drug. It is a plant with hundreds of compounds. Each of them could have a unique effect on our health. But we are only just beginning to scratch the surface of what those effects look like because the drug was widely illegal for decades, experts say.

Marijuana's benefits could include relief for the symptoms linked with serious health conditions, from pain and nausea to digestive issues and seizures. At the same time, its risks might include addiction, reduced cognitive performance, and CHS.

"We must recognize that the full range of potential adverse health consequences from cannabis consumption are not fully understood," Dr. Nora Volkow, the director of the National Institute on Drug Abuse, wrote recently in a major medical journal.

CHS could affect millions of Americans, but we don't know much about it

In interviews that Business Insider conducted with doctors, researchers, and more than half a dozen people who have symptoms of CHS, people painted a picture of a severe but still mysterious illness. Some researchers estimate it could affect millions of Americans; others hope it is less common.

Because marijuana remains illegal on the federal level and the condition was only recently identified, exact numbers on how many people have CHS are difficult to pin down.

The syndrome appears to affect people who consume marijuana heavily across all backgrounds, ages, and genders. Most say they've consumed cannabis several times a day for between two years and up to multiple decades. They describe a condition that appears suddenly and without warning, sometimes hours after marijuana consumption.

For people who've been using marijuana for years, it's as if a switch gets flipped. After the first occurrence, every time someone with CHS uses cannabis, they risk becoming violently ill. Using pesticide-free marijuana, edibles, concentrates, CBD-only products, or vape pens doesn't make a difference, they say.

In some cases, as with other chronic conditions, CHS appears to cause flare-ups that are difficult to predict. Patients can sometimes go weeks without symptoms and then suddenly suffer a particularly intense bout.

Many people with the condition end up in emergency rooms or urgent-care centers, and some are admitted to the hospital. Complications can range from mild to severe and include problems such as infections, kidney failure, and significant weight loss.

If left untreated, CHS can be deadly.

'People don't relate it to marijuana'

Moon in 2017, before she was diagnosed with CHS. Courtesy of Alice Moon Initially, Moon was hesitant to believe that her illness was related to marijuana.

She'd been using the drug for half a decade with no symptoms. To make things more perplexing, she had first turned to cannabis as a way to relieve occasional pain and nausea linked to things such as menstrual cramps. Doctors say Moon isn't alone in her initial disbelief.

"People don't relate it to marijuana because they’ve been smoking for decades" with no recognizable issues, said Dr. Joseph Habboushe, an associate professor at New York University Langone Health and the lead author of a study on the condition published last year.

Moon had been using various forms of marijuana (edibles, concentrates in vape pens, and several strains of the flower form) daily for about three years. Then one day in 2016, several hours after smoking part of a joint, she ended up bowled over with nausea.

After that, she’d get sick to her stomach roughly every month or so. Thinking that alcohol might have something to do with her symptoms, she quit. It didn't help.

She tried improving her diet. Nothing worked. Eventually, she wound up in an urgent-care center, where doctors diagnosed her with heartburn.

Moon's symptoms continued for more than a year. The only thing that helped was spending hours in a steaming-hot bath.

In 2018, things took a turn. She was throwing up every week. A specialist she saw around that time said it could be CHS and told her the cure was to quit using marijuana. She didn't want to believe it, but she decided she needed to try quitting.

But before giving it up, she went to one last cannabis event. Moon described it as her last supper.

Moon spent that evening — and most of the next two weeks — in the bathroom. Every day, her vomiting was so bad she felt like she could barely come up for air. One morning, she was so weak that she passed out on her front lawn. At that point, she'd had enough.

'I was in denial. I didn't want to believe it was true.'

She quit marijuana completely for three months and was symptom-free. Then she tried CBD, hoping there was some form of cannabis she could enjoy. One day she took 200 milligrams of CBD in capsules. That night, she ended up in the ER.

Within about a week in the ER, Moon developed three ulcers, a hernia, and an infection. She dropped 12 pounds from her already slender frame, missed Christmas with her family and New Year's with her friends.

"I looked like I was dying," she recalled.

In Colorado, CHS was a leading driver of ER visits between 2012 and 2016. Leonard Ortiz/Digital First Media/Orange County Register via Getty Images

In Colorado, where marijuana is legal, CHS was recently identified as one of the leading drivers of emergency-room visits tied to cannabis.

For a study published last month, researchers looked at ER visits between 2012 and 2016 and concluded that stomach issues such as nausea and vomiting were the main cause of the trips, ahead of reasons such as intoxication and paranoia. Of the stomach issues, CHS was the most commonly reported problem.

"CHS is certainly not very rare," Dr. Andrew Monte, the lead author on the study and an associate professor of emergency medicine at UCHealth University of Colorado Hospital, told Business Insider. "We see it absolutely every week in our ER."

For Moon, it took a CT scan, an MRI, and an endoscopy to rule out other issues before she took her doctor's initial diagnosis to heart: She had CHS, and she had to stop consuming marijuana.

"I was in denial. I didn’t want to believe it was true," she said. "Cannabis is my world. It's my whole life."

Hot showers give temporary relief, but the only cure is quitting

Researchers first began describing the symptoms of CHS in the early 2000s, but it was not until recently that doctors in different hospitals around the world began defining it as a unique syndrome. Initially, it was often lumped in with other digestive conditions that share some of its features, such as cyclic vomiting.

It is still unknown how many cases of cyclic vomiting could actually be CHS, Habboushe said. Conversely, it’s also possible that some cases of CHS are something else entirely. Complicating things further, some people initially turn to marijuana to help with their nausea and vomiting. (The federally approved THC-containing drug Marinol is prescribed to treat the nausea and vomiting caused by treatments for cancer and AIDS.)

One of CHS's most distinctive features is the tendency for patients to use hot baths or showers to temporarily relieve the symptoms. Other standard remedies for nausea, such as anti-nausea medications, don't work.

Habboushe believes heat helps because of something to do with the way CHS interferes with the body's natural temperature and pain controls. For some reason, hot water signals to the body that everything is okay, and the pain and nausea from CHS subside for at least as long as the water remains scalding.

"It was this need to be swaddled," Susie Frederick, a 30-year-old Portland resident who was told she might have CHS last year, told Business Insider. "That feeling of needing comfort all over."

Frederick asked Business Insider not to use her real name because she works in the cannabis industry.

Experts say that as a more comprehensive picture of cannabis' potential health benefits is beginning to take shape, a complete understanding of its risks is also coming to light. Associated Press

Frederick is unsure whether her symptoms are CHS or something else, perhaps something linked to hormonal changes. She has a history of other digestive issues, head injuries, and problems with her gallbladder, which complicate things.

Frederick said her episodes of vomiting and nausea tend to happen when she's on her menstrual cycle and when she's traveling or dealing with added stress. She had her first episode after she got a small upper-arm birth-control implant, which releases the hormone progestin to prevent pregnancy.

"It’s hard for me to say distinctly that CHS is actually what's happening. It does mimic quite a few other things," Frederick said.

The nausea linked to CHS appears to be stronger and more intense than the typical nausea linked to things such as motion sickness or pregnancy, according to patients.

Barry Howard, a 28-year-old chef in Birmingham, Alabama, said what struck him most about his CHS was the feeling that he urgently needed to rid his body of something, such as a toxin. Business Insider isn’t using Howard’s real name because he lives in a state where cannabis is illegal.

"It’s not a normal, 'Oh, I’m sick to my stomach' feeling. You feel like your insides want to come out — like you’re trying to push something out," Howard told Business Insider.

Brian Smith died of dehydration after struggling with CHS for months

If someone with CHS keeps using marijuana, severe complications may unfold. In one case, a 17-year-old in Indiana named Brian Smith died after struggling with CHS for more than six months.

Regina Denney, Smith's mother, told Business Insider that Smith was first diagnosed with CHS in an emergency room in spring 2018. On the way to the hospital, he had been vomiting so badly that she had to pull to the side of the road about five times.

At the ER, doctors told Denney that her son was severely dehydrated and warned her that his kidneys, the body's natural toxin-filtering system, were on the verge of shutting down.

At first, Denney thought his symptoms were related to the heartburn he'd been diagnosed with at age 10, which they'd been treating for years with doctor-prescribed medications such as Prilosec.

After putting Smith on fluids and running a series of tests, they decided to keep him in the hospital overnight.

While waiting on the results, a doctor asked Smith if he smoked marijuana. When he said yes, the doctor said she thought he had CHS. The doctor said CHS is caused by cannabis, and she told Smith the cure was quitting. She didn't say it could be deadly.

'All we'd ever heard about marijuana were the benefits'

Like others diagnosed with CHS, Smith was somewhat doubtful. He'd been using marijuana for years without problems. Nevertheless, he agreed to stop until he saw a specialist.

"All we’d ever heard about marijuana were the benefits," said Denney. "How it helps nausea, how it helps appetite."

The specialist, a gastroenterologist, confirmed the ER doctor's diagnosis a few days later and didn't run any additional tests. He said Smith had CHS and needed to stop using marijuana. Although Smith and his mom still had their doubts, she urged him to stop smoking.

The next two months were excruciating for Denney. Although her son had stopped vomiting — at least as far as she could tell — he continued to lose weight. He also occasionally complained about nausea. At first, she assumed it was related to his heartburn. But one day when she noticed his shoulder blades poking out from the thin cotton of his T-shirt, she began to suspect he was using cannabis again.

"He was skin and bones," Denney said.

Then one night, Denney got up in the middle of the evening to find her son on the couch in the living room holding his stomach. He said he didn't feel good. The next morning, he started vomiting violently. Between sprints to the bathroom, where she'd bend over to hold a bucket under her son and rub his back, and the kitchen, where she was making dinner for her infant grandson, Denney called the doctor.

They'd send some medicine for her to pick up at the pharmacy, they said. But when Denney picked it up, it was the same anti-nausea medication he'd gotten at the ER. After she told the doctor that the medicine they ordered didn't work, they said they would order something else. In the meantime, she went back home.

All of a sudden, at home, Smith collapsed. He grabbed his back, near his kidneys, then his chest. He told his mom he couldn't breathe. Denney immediately called 911.

By the time the paramedics arrived, Smith had stopped breathing. They tried CPR. Smith was pronounced dead half an hour later.

On her birthday, Denney received her son's coroner's report. When Smith died, he had been severely dehydrated, according to the document. The cause of death on the report, which Business Insider viewed, read "dehydration due to CHS."

Denney couldn't believe it.

"I said marijuana couldn't have killed my son. It doesn’t take people’s lives," she said.

When Denney was cleaning out her car a few days after Smith died, she pulled her son's backpack from the backseat. Inside, she found an unsealed baggy of edibles that looked like candy.

"I have to do something to make people aware," Denney said. "I don’t want anybody to have to go through this. No parent should have to lose a child, especially to something like this."

'People say I work for the feds'

Some people with CHS are hesitant to talk about the condition out of fear that they’ll be viewed as opposed to marijuana and efforts to legalize the plant. Moon and Howard said they got significant pushback from friends, family members, and other people in their communities when they told them about CHS.

After Moon shared an article that someone recently published about her experience with the condition, her inbox was flooded with hate mail.

"People say I work for the feds. People say I should leave the industry," she said.

Clinicians and researchers are studying marijuana compounds for their potential ability to treat dozens of ailments, and there's already a cannabis-based drug to curb epileptic seizures.

But, at the same time, as research into cannabis' potential benefits continues, a dicey marijuana-as-a-cure-all trend has sprouted. As they seek to take advantage of the growing public perception of cannabis as universally beneficial, hundreds of companies are hawking everything from CBD-based lotions and drinks to cupcakes and candy — many of them without research to support their claims.

At the same time that solid research into cannabis' potential benefits continues, a dicey marijuana-as-a-cure-all trend has sprouted. By Chloe/Leslie Kirchoff

People such as Moon, Frederick, and Howard — people who turned to marijuana because they said it helped with other health issues — appear to be caught in the middle. Frederick began using cannabis for sports injuries and said she also used it to help her transition off a high dose of antidepressants and anti-anxiety medications.

Howard first turned to marijuana because he thought its therapeutic qualities outweighed its risks.

Howard, who was working toward a college scholarship, had played soccer competitively in high school when he developed a compression fracture in his lower back. The injury left him with lifelong pain. Wanting to avoid opioid painkillers out of concern he'd become addicted, he turned to cannabis.

"If anything, I thought [marijuana] was helping what I was going through," Howard said.

'This doesn't mean marijuana is bad or good'

Monte and Habboushe emphasized that most CHS patients are using very high levels of marijuana — far higher than what they’d consider standard or "recreational" use. To them, that suggests that while CHS is severe, it may also be avoidable with moderate cannabis consumption.

"Using in moderation is probably the best answer to help people avoid this," Monte said. "People who are using 10 times a day are likely at a high risk. Even just daily use is probably too much, unless you’re doing it for medical purposes."

Despite her struggle with CHS, Moon hasn't left the marijuana industry. She no longer reviews cannabis products, having given up any form of the drug, including CBD. Today, she works for multiple marijuana companies and serves as the head of public relations for a cannabis tech startup called Paragon.

"I'm passionate about cannabis, and I believe in its healing properties. But I also recognize that maybe I’ve had too much," she said.

Since her son Brian's death, Regina Denney has created her own Facebook group in his memory. She hopes to raise awareness about CHS.

"My goal is to bring something positive out of the heartbreak," she said.