About 10 percent of those surveyed said they frequently or almost always feel sad after sex, LiveScience.com reported Thursday.
"Under normal circumstances, the resolution phase of sexual activity, or [the] period just after sex, elicits sensations of well-being, along with psychological and physical relaxation," study author Robert Schweitzer of the Queensland Institute of Technology said.
"However, individuals who experience postcoital dysphoria [sadness] may express their immediate feelings after sexual intercourse in terms of melancholy, tearfulness, anxiety, irritability or feeling of restlessness," he said.
Although prior sexual abuse can cause such feelings in subsequent sexual encounters, Schweitzer said, his research found only a moderate correlation between the two.
"This suggests other factors, such as biological predisposition, may be more important," Schweitzer said.
The study was published in the International Journal of Sexual Health.