A Northwestern University study says that young gay men in serious relationships are less likely to practice safe sex than those who have casual sex, despite still being at risk of unknowingly being HIV positive. Brian Mustanski of the NU Feinberg School of Medicine says about 80 percent of gay young men who are HIV positive don't know it, because they aren't being tested frequently enough.

“It isn't enough to ask your partner his HIV status," Mustanski says. "Instead, both people in a serious, monogamous couple relationship should go and receive at least two HIV tests before deciding to stop using condoms.”

The study was published in the journal Health Psychology. It recommended that HIV prevention programs should be directed toward those in serious relationships rather than those individuals who have casual sex.