Accepted norms of sexual behavior and attitudes vary greatly within and among different cultures.

Generally, what is normal and abnormal cannot be defined readily. However, when sexual behavior or difficulties bother a person or their partner or cause harm, treatment is warranted.

Societal attitudes about sexuality also change with time, as has occurred with the following:

Masturbation: Once widely regarded as a perversion and a cause of mental disorders, masturbation is now recognized as a normal sexual activity throughout life. It is considered abnormal only when it inhibits partner-oriented behavior, is done in public, or is sufficiently compulsive to cause distress. About 97% of males and 80% of females masturbate. Although masturbation is harmless, guilt created by the disapproval and punitive attitudes of other people may cause considerable distress and impair sexual performance. Masturbation often continues at some level even in a sexually healthy relationship.

Homosexuality: Homosexuality has not been considered a disorder by the American Psychiatric Association for > 3 decades. About 4 to 5% of the population identify themselves as exclusively homosexual for their entire lives. Like heterosexuality, homosexuality results from complex biologic and environmental factors leading to an ability to become sexually aroused by people of the same sex. Like heterosexuality, homosexuality is not a matter of choice.

Promiscuity: Frequent sexual activity with many partners, often involving anonymous or one-time-only encounters, may indicate a diminished capacity for intimacy. However, promiscuity is not in itself evidence of a mental disorder. Casual sex is common, although the fear of AIDS, herpes simplex infections, and other sexually transmitted diseases has resulted in a decrease.

Extramarital sex: Most cultures discourage extramarital sexual activity but accept premarital or non-marital sexual activity as normal. In the Western world, most people engage in sexual activity before marriage or without marriage as part of the trend toward more sexual freedom in developed countries. Extramarital sex occurs frequently among married people despite social taboos. This behavior has the potential to pass diseases to unsuspecting spouses.

Full story at; Merk website

Related Reading:

Family
Human Biology - Sexuality
Sexualities: Identities, Behaviors, and Society
Erotic Tales - Lesbian Encounters