A bad psychedelic trip might have long-term consequences for a person’s mood, researchers say.

Folks who land in the hospital due to hallucinogens are six times more likely to be diagnosed with mania within a few years, according to results published Dec. 2 in the journal PLOS Medicine.

“Our study showed a strong association between hallucinogen use that requires care in the emergency room or hospital and future risk of mania and bipolar disorder,” lead researcher Dr. Daniel Myran, a family medicine, preventative medicine and public health physician with North York General Hospital in Canada, said in a news release.

Hallucinogens like ketamine, LSD and psilocybin have become more popular in recent years, both as recreational drugs and for treatment of conditions like depression or post-traumatic stress disorder, researchers said in background notes.

But there have been concerns that the drugs might cause manic behavior or bipolar disorder in people with a high risk for those sorts of mood problems, researchers said.

“There has been a large increase in interest in the use of hallucinogens, often paired with therapy, to treat some mental health disorders,” Myran said. “The current study helps highlight that hallucinogen use outside of trial settings may have important risks for a subset of people who use them.”

For the new study, researchers analyzed records of nearly 7,300 patients treated in a hospital or ER for hallucinogen use, comparing them to more than 78,000 people hospitalized for other causes.

Those treated for hallucinogen use had a six-fold higher risk of needing treatment for mania within the next three years, researchers found.

They also were four times more likely to be diagnosed with bipolar disorder, results show.

This increased risk of mania and bipolar disorder is comparable to that faced by people treated in a hospital for cannabis overuse, researchers said.

However, researchers think hallucinogen use likely exposes a greater risk of mood disorders that already existed in these patients, rather than the psychedelics directly causing later manic episodes.

“Our results fill an important gap around the complexity of therapeutic versus safety profile of hallucinogen use,” senior researcher Dr. Marco Solmi, an associate professor of psychiatry with the University of Ottawa in Canada said in a news release. “Future projects will need to identify predictors of beneficial versus harmful outcomes at the individual level.”