Sex can leave a woman feeling refreshed and satisfied. But for some women, it can also leave them feeling down in the dumps. It's not necessarily because the sex was bad. Feelings of depression and anxiety immediately following sex —even good sex — is a real condition that's a lot more common than you think.

Nearly half of women have experienced post-coital dysphoria, a condition that causes feelings of melancholy, agitation, tearfulness, anxiety, or aggression right after sex, according to a recent studypublished in the Journal of Sexual Medicine. About 46 percent of sexually active female college students in the study reported feeling symptoms of post-coital depression during some point in their lives. Five percent of the women said that they had experienced symptoms several times within the previous four weeks.

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Anxiety and depression can accompany one-night stands. But researchers at the Queensland University of Technology found that the level of intimacy between sexual partners was irrelevant.

It is not clear what causes women to get the "post-sex blues." Researchers theorized that "hormonal shifts which occur after an orgasm, which can also trigger post-coital headaches, could be to blame," the Independent reported.

Lead researcher Robert Schweitzer and his colleagues conducted a similar study in 2011. That study revealed that 32.9 percent of women surveyed reported feeling post-coital depression symptoms, and almost 10 percent reported feelings of "distress and depression following consensual sex," Medicine Daily reported.

"The findings build upon our previous research investigating the correlates of sexual functioning women," Schweitzer said. "The results of our original research in this area have now been confirmed in an international multinational study on negative post-coital emotions, which appear to have evolutionary functions."

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