Until recently, most theorists and therapists tended to view homosexuality as a deviant or aberrant form of behavior — a view still widely held by the general public and by certain religious groups.

Cross-cultural evidence demonstrates that same-sex behavior in many societies may be regarded as different but not morally defective or psychologically abnormal.

Socially-Institutionalized Homosexuality
Indeed, various indigenous groups, such as the Sambia on the island of New Guinea, actually have a form of socially-institutionalized and approved form of homosexuality in which adolescent males engage in same-sex acts, such as fellatio, before marrying a woman and rearing a family. Some males may choose to restrict their behavior to same-sex acts after adolescence and some married males may occasionally engage in same-sex acts.

By contrast, Western psychology and psychiatry, at least until relatively recently, have tended to regard same-sex behavior as abnormal and the product of inappropriate gender socialization.

Although Freud argued that humans are born with a bisexual nature which in time becomes mediated by culture, the American Psychiatric Association up until 1973 had designated homosexuality as a pathological form of behavior. The Association lifted its claim that homosexuality is abnormal in 1974, and now maintains that there is no scientific evidence that demonstrates the effectiveness of any therapies that attempt to transform homosexuals into heterosexuals.

In 1994, the American Medical Association, a traditionally conservative organization, called for "a non-judgmental recognition of sexual orientation by physicians."

Causes of Same-Sex Orientation Controversial
While the causes of homosexuality as a sexual orientation remain controversial, many sex researchers believe that it may be the product of a complex interaction of sociocultural and biological factors.

While the evidence still remains highly tentative, there is cause to believe that some individuals exhibit a greater biopsychological predisposition to engage in same-sex acts than others.