Researchers in the School of Medicine & Health Sciences found cannabis use during adolescence led to more emergency department visits linked to the drug in a report published late last month.
Andrew Meltzer, a professor of emergency medicine at the SMHS and the study’s lead author, said he and his colleagues distributed an internet-based survey to people suffered from a condition called cannabinoid hyperemesis syndrome, in which a patient experiences cyclical nausea, vomiting and abdominal pain after using cannabis. The study found that those who started cannabis use in adolescence had higher odds of emergency department visits, with Meltzer saying CHS-related emergency department visits have gone from “very rare” to “relatively common” due to increased cannabis use among young people.
“We’re trying to understand more about the people that suffer from this disease, so we’re trying to find a way to efficiently collect data about people suffering,” Meltzer said. “So this is a relatively new disease that’s been described only for the past 20 years and something that we see commonly in the emergency department, but there’s limited research on it.”
The study found 85 percent of the 1,052 participants reported at least one emergency department visit because of CHS and 44 percent reported having been hospitalized at least once with the CHS symptoms. Meltzer said adolescents have started to use cannabis in higher numbers due to the drug being legalized in more places and information being spread claiming it has no side effects, which he said is true for those who use cannabis occasionally, but effects become more severe for chronic users. A study from the New York University School of Medicine found 33 percent of chronic marijuana users met the criteria for CHS.
According to 2025 DISA Global Solutions Inc., marijuana laws have been rapidly changing at the state level since Colorado and Washington legalized the drug in 2012, with each state assessing their own laws and regulations on cannabis use. As of Jan. 1, 2025, 24 states and the District of Columbia have legalized marijuana, 20 states have mixed legalization and six states have established it as fully illegal.
“There’s a lot of information out there that cannabis has no side effects, that it’s considered medicine for some things, but for the most part, side effects are relatively minimal if you use it sporadically, but we don’t really know what happens when people use it regularly and in high doses,” Meltzer said.
Meltzer said the research team was able to confirm that prolonged exposure to cannabis and daily or near daily use was common before developing CHS. Additionally, patients who start using cannabis in adolescence tend to have more severe CHS, in which severity is defined by a need for patients to have emergency department visits or hospitalizations.
“We’re trying to understand more about the epidemiology, including the exposure to cannabis required, the duration of cannabis, the frequency of cannabis use before you develop the syndrome,” Meltzer said. “We’re trying to understand a little bit about risk factors regarding severity of CHS, so different things that might make people suffer more or less.”
Aditya Loganathan, a research coordinator for the study, said he helped create the survey, review for the research approval process to ensure that the survey was ethical to use and conduct outreach in social media groups used to find participants for the study.
Loganathan said the study reflects the increased popularity of marijuana use and that many people who report experiencing negative symptoms originally started using marijuana to reduce things like nausea and end up with worse effects. The amount of people reporting daily or near-daily marijuana use increased 15-fold between 1992 and 2022, according to the National Survey on Drug Use and Health.
“Now with marijuana being way more popular and all this, it’s important to really understand the long term effects,” Loganathan said. “And I think Dr. Meltzer was best when he said it like a lot of people get this prescribed cannabis to reduce nausea, so it’s interesting to see how it actually causes the inverse effects and creates that paradoxical interaction.”
Loganathan said the process of data collection started with the first participant on Feb. 24, 2023, and the last participant on July 18, 2023. Researchers distributed the survey links through CHS support groups on Facebook and Reddit using REDCap survey software, restricted to individuals that had a history of CHS.
Loganathan said researchers chose to distribute the survey through support groups because they wanted people who were diagnosed with CHS to get more accurate results, instead of people who just suspected they had it.
Loganathan said the study is useful to combat misinformation about the health effects of marijuana, which he said was prevalent.
“I know a lot of people who smoked a lot of weed, and I know a lot of people who still use and people always say stuff, and there’s a lot of misinformation,” Loganathan said. “So it’s nice to see that there’s a lot of information coming out that’s scientifically backed, and is promoting the conversation.”
Rosalie Liccardo Pacula, a professor and economist at the University of Southern California, said youth who initiate use of cannabis early are far more likely to become addicted because the brain is still developing.
“The adolescent brain is still developing, and we know that there’s numerous cannabinoid receptors in the brain, far more than opioid receptors as a matter of fact,” Pacula said. “And so the implication is that the significant, more persistent use during adolescence and actually rewiring the brain even more so than nicotine or opioids, and we want to understand that.”
Pacula also said there is a desire in the research community to impose caps, the maximum amount of THC that a consumer could have in a product and clearly identify caps to consumers. THC, also known as delta9-tetrahydrocannabinol, is believed to be the main ingredient that produces the psychoactive effect in cannabis products.
“Some states, people might not be aware of this, some states actually require that the edibles contain no more than five milligrams THC, while the vast majority of states that have legalized them allow up to 10 milligrams,” Pacula said. “Most consumers aren’t aware that that’s a difference.”
