The finding that women who do not use condoms during sex are less depressed and less likely to attempt suicide than are women who have sex with condoms and women who are not sexually active, leads one researcher to conclude that semen contains powerful—and potentially addictive—mood-altering chemicals.

Study author Gordon G. Gallup, Ph.D., a psychologist at the State University of New York in Albany, also found that women who routinely had intercourse without condoms became increasingly depressed as more time elapsed since their last sexual encounter. There was no such correlation for women whose partners regularly used condoms.

Gallup’s survey of 293 college women also found that those who did not use condoms were most likely to initiate sex and to seek out new partners as soon as a relationship ended. “These women are more vulnerable to the rebound effect, which suggests that there is a chemical dependency,” says Gallup.