British health specialists are warning about a trend called “chemsex,” which refers to intentional sex under the influence of psychoactive drugs, mostly among men who have sex with men. Chemsex sessions often last several hours to several days, with multiple sexual partners.

Chemsex participants report an average of five sexual partners per session. Unprotected sex is the norm, the researchers reported in an editorial in the British Medical Journal.

The researchers say people who engage in chemsex often describe not sleeping or eating for up to 72 hours, which can harm their health. “Users may present [symptoms] too late to be eligible for post-exposure prophylaxis for HIV transmission,” they wrote. “An increased number of sexual partners may also increase the risk of acquiring other sexually transmitted infections.”

People engaging in chemsex often use the drugs mephedrone (also known as “meow meow,”) GHB, GBL and crystal meth, The Washington Post reports. Participants say using the drugs reduces their inhibitions and increases pleasure. “Mephedrone and crystal meth can create a powerful psychological dependence, with GHB/GBL creating a dangerous physiological dependence,” the researchers warn.

“Some users report using them to manage negative feelings, such as a lack of confidence and self esteem, internalised homophobia, and stigma about their HIV status,” the researchers wrote.

One of the editorial’s co-authors, Hannah McCall, told the newspaper she did not consider engaging in chemsex to be outlandish behavior. “A lot of people having chemsex make informed decisions, just as people using alcohol make informed decisions,” she said.

Health officials want to make sure participants know the risks and can protect themselves. McCall noted other communities may take up the practice. “A lot of drug trends start in gay men’s community and spread to mainstream society,” she said. “I wouldn’t be surprised if it is already happening.”