The study, which is bound to provoke controversy, showed that the women who were directly exposed to semen were less depressed. The researchers think this is because mood-altering hormones in semen are absorbed through the vagina. They say they have ruled out other explanations.

The question many people will ask is whether oral sex could have the same mood-enhancing effects. "Since the steroids in birth control pills survive the digestion process, I would assume that the same holds true for at least some of the chemicals in semen," Gallup says.