As men who have sex with men (MSM) have increasingly become aware that successfully treating HIV prevents the spread of infection, this knowledge may have contributed to falling condom use rates among them.

Publishing their findings in the Archives of Sexual Behavior, researchers reviewed data from surveys conducted among 1,831 MSM at the Atlanta Gay Pride Festival in 1995, 2005, 2006 and 2015. The surveys asked the respondents about substance use, sexual behavior, including condom use, beliefs about HIV treatment and beliefs about sexual risks in relation to a sexual partner’s HIV treatment status.

Among respondents who were HIV negative or had an unknown HIV status, the proportion reporting any condomless anal sex during the previous six months increased from 43 percent in 1997 to 51 percent in 2005, 49 percent in 2006 and 61 percent in 2015. The corresponding figures for the HIV-positive respondents were 25 percent, 50 percent, 61 percent and 67 percent.

Among the HIV-negative or unknown-HIV-status respondents, the proportions reporting condomless sex with two or more partners during the previous six months were 9 percent in 1997, 19 percent in 2005, 18 percent in 2006 and 33 percent in 2015. The corresponding figures among the HIV-positive respondents were 9 percent, 33 percent, 39 percent and 52 percent.

Among the HIV-negative or unknown-HIV-status respondents, the average reported proportion of sexual acts involving condoms during the previous six months were a respective 56.7 percent in 1997, 56.2 percent in 2005, 52.8 percent in 2006 and 38.7 percent in 2015. The corresponding figures for the HIV-positive respondents were 82.1 percent, 50.2 percent, 42 percent and 47.6 percent.

Over time, there was a decline in the overall perceived risk of transmitting the virus through condomless anal sex with an HIV-positive man with an undetectable viral load. In later years of the survey, respondents who had condomless sex were more likely to endorse beliefs that HIV treatment protects against transmission of the virus. Those who engaged in condomless anal sex reported significantly lower perceived risks of contracting HIV when a partner has an undetectable viral load.

HIV-positive men who reported condomless anal sex reported the lowest perceived risks associated with having an undetectable viral load, while HIV-positive men who did not report condomless anal sex had the highest perceived risks of transmission of the virus in this context.

“Thus,” the study authors wrote, “as treatment-related beliefs continue to shift in gay communities, we may expect further increases in condomless anal sex.”

“Treatment-related behavioral beliefs in this study paralleled a resurgence in condomless anal sex among men who have sex with men measured over nearly two decades,” Seth Kalichman, PhD, a professor of psychology at the University of Connecticut and the study’s lead author, said in a press release. “The current study adds to the mounting evidence that substantial changes have occurred in community-held beliefs that condomless anal sex is safer in the era of HIV treatment as prevention.”

To read a press release about the study, click here.

To read the study abstract, click here.