Sexual dysfunction occurs during any phase of the sexual response cycle (traditionally desire, arousal, plateau, orgasm, and resolution) that prevents the individual or couple from experiencing satisfaction from the sexual activity. Sexual dysfunction is typically classified into four categories: Desire disorders —lack of sexual desire or interest in sex; Arousal disorders —inability to become physically aroused or excited during sexual activity; Orgasm disorders —delay or absence of orgasm (climax); Pain disorders — pain during intercourse.
Human sexual disorders are not to be confused with disorders or differences of sex development (DSDs), which are medical conditions involving the reproductive system
Age-associated sexual dysfunction in both men and women is frequently tied to chronic illnesses, such as arteriosclerosis ("hardening of the arteries"), hypertension, diabetes, and depression. Other causes include prostate enlargement (in men); endometriosis, fibroids, and PMS (in women); and age-related declines in hormone levels in both sexes. Sexual dysfunction is also a common side effect of many prescription and over-the-counter drugs, including those for depression, high blood pressure, insomnia, and allergies.