Masturbation is the sexual stimulation of one's own genitals for sexual arousal or other sexual pleasure, usually to the point of orgasm. Studies have found that masturbation is frequent in humans of both sexes and all ages, although there is variation. Various medical and psychological benefits have been attributed to a healthy attitude toward sexual activity in general and to masturbation in particular. No causal relationship is known between masturbation and any form of mental or physical disorder. Masturbation has been depicted in art since prehistoric times and is mentioned and discussed in very early writings. In the 18th and 19th centuries, some European theologians and physicians described it as "heinous", "deplorable", and "hideous", but during the 20th century these taboos generally declined.