Young men and women who suffer from depression are much more likely than their non-depressed peers to have multiple sex partners in a given year, new research suggests.

And for black men - but not black women, or white men or women - being depressed also increases the likelihood of contracting a sexually transmitted infection (STI), Dr. Maria R. Khan of The University of North Carolina at Chapel Hill and her colleagues found.

The findings are based on 8,794 participants in the National Longitudinal Study of Adolescent Health, which began in 1995, when participants were in 7th to 12th grade.

The researchers determined that close to 20% of black women were recently or chronically depressed in adulthood, as were 11.9% of black men, 13% of white women and 8.1% of white men.

For both genders and among blacks and whites, being depressed was associated with a greater likelihood of having multiple sex partners, although it didn’t have an effect on whether or not people used condoms.

But black men were the only group for whom recent or chronic depression increased the likelihood of an STI; before adjusting for other factors, depressed black men were nearly twice as likely to contract an STI, while after the researchers adjusted for age, education level, income and other factors, the relationship got even stronger, with chronically depressed black men being at triple the risk of an STI.

However, the fact that depressed black men had more sex partners didn’t account for their greater STI risk, the researchers say. The study wasn’t designed to investigate what other mechanisms might be responsible, they point out; it’s possible depressed black men were more likely to engage in types of risky sex that weren’t looked at in the study, or they may have “high-risk social and sexual networks” compared to non-depressed black men. “This may be the case, in part, because depression is strongly associated with substance use, and substance users have networks with high levels of STI,” the researchers say.

US youth who are depressed are known to be more prone to risky sexual behavior, and to developing STIs, Khan and colleagues note in the Archives of Pediatrics and Adolescent Medicine.

“This study provided further evidence that US youth at high risk for STI also experience a disproportionate risk of depression, highlighting the need for improved integration of mental health and STI diagnosis, treatment, and prevention,” the researchers write. “Black youth should be a priority when allocating resources to improve mental health care.”

SOURCE: Archives of Pediatrics and Adolescent Medicine, July 2009.