“Omne animal triste post coitum” Aristotle
Post-coital tristesse (PCT) is a feeling of melancholy after sexual intercourse (coitus). Its name comes from New Latin postcoitalis and French tristesse, literally "sadness". Many PCT sufferers may also exhibit strong feelings of anxiety, anywhere from five minutes to two hours after coitus.
The phenomenon is famously traced to the Greek doctor Galen, who wrote, "Every animal is sad after coitus except the human female and the rooster." The philosopher Baruch Spinoza in his Tractatus de Intellectus Emendatione writes "For as far as sensual pleasure is concerned, the mind is so caught up in it, as if at peace in a [true] good, that it is quite prevented from thinking of anything else. But after the enjoyment of sensual pleasure is past, the greatest sadness follows. If this does not completely engross, still it thoroughly confuses and dulls the mind."
PCT is a separate phenomenon from the refractory period, the period after an orgasm where it is impossible for a person to have additional orgasms, especially after ejaculation. PCT is different in that it occurs only after sexual intercourse and does not require an orgasm to occur, and in that its effects are primarily emotional rather than physiological.
Some doctors prescribe serotonin reuptake inhibitors, such as Prozac, Zoloft, to treat PCT. After two weeks, patients reported that, "while sex was less intensely pleasurable, no emotional crash followed.”