An ongoing study in New York City that focused on gay and bisexual men has found that individuals taking pre-exposure prophylaxis (PrEP), a preventative HIV medication, report more condomless sex with casual partners. 

The study was conducted by researchers from the Center for HIV Education Studies and Training (CHEST) at Hunter College in NYC. 1,071 HIV-negative young men over the age of 18 were studied from 2014 to 2016. 

It was found that participants used PrEP at increased rates over the duration of the study, as well as a statistically significant increase in reported condomless anal sex with partners. According to researchers, participants who reported currently being on PrEP had a 2.52-fold higher rate of casual condomless sex than time when they did not report current PrEP use. 

Also, participants who reported current PrEP use had a 12.38-fold higher rate of condomless sex with HIV-positive partners than at times when they were not taking the preventative. 

Participants who went off PrEP during the study had a 12 percent lower rate of recent casual condomless sex than when they were on the treatment. 

The researchers also found a correlation with higher STI rates in participants on PrEP. It was found that these men were 58 percent more likely to receive an STI diagnosis at the time they reported active PrEP use and 22 percent more likely after recently stopping PrEP use. 

PrEP drastically lowers the chances of HIV transmission, but does not lower rates of other STIs, making intercourse with condoms the best way to prevent STIs. 

It was decided by the researchers, however, that larger studies of individuals with less risky sexual patterns while on PrEP are needed to determine how the drug may affect behavioral patterns and STI diagnoses.