The field of psychology has extensively studied homosexuality as a human sexual orientation. The American Psychiatric Association listed homosexuality in the Diagnostic and Statistical Manual of Mental Disorders (DSM) in 1952, but that classification came under scrutiny in research funded by the National Institute of Mental Health. That research and subsequent studies consistently failed to produce any empirical or scientific basis for regarding homosexuality as anything other than a natural and normal sexual orientation that is a healthy and positive expression of human sexuality. As a result of this scientific research, the American Psychiatric Association declassified homosexuality as a mental disorder in 1973. Upon a thorough review of the scientific data, the American Psychological Association followed in 1975 and also called on all mental health professionals to take the lead in "removing the stigma of mental illness that has long been associated" with homosexuality. In 1993, the National Association of Social Workers adopted the same position as the American Psychiatric Association and the American Psychological Association, in recognition of scientific evidence. The World Health Organization, which listed homosexuality in the ICD-9 in 1977, removed homosexuality from the ICD-10 which was endorsed by the 43rd World Health Assembly on 17 May 1990.
The consensus of scientific research and clinical literature demonstrate that same-sex attractions, feelings, and behaviors are normal and positive variations of human sexuality. There is now a large body of scientific evidence that indicates that being gay, lesbian, or bisexual is compatible with normal mental health and social adjustment.
Historical background
The view of homosexuality as a psychological disorder has been seen in literature since research on homosexuality first began; however, psychology as a discipline has evolved over the years in its position on homosexuality. Current attitudes have their roots in religious, legal, and cultural underpinnings. Some Ancient Near Eastern communities, such as the Israelites, had strict codes forbidding homosexual activity, and this gave way to later usage of the same texts by the original missionaries of Christianity, who themselves descended from the tribes of Israel; Paul in particular is notable for his allusion to and reinforcement of such texts in his letters to nascent churches. Later, the Apostolic Fathers and their successors continued to speak against homosexual activity whenever they mentioned it in their (surviving) writings. In the early Middle Ages the Christian Church ignored homosexuality in secular society; however, by the end of the 12th century, hostility towards homosexuality began to emerge and spread through Europe's secular and religious institutions. There were official expressions condemning the "unnatural" nature of homosexual behavior in the works of Thomas Aquinas and others. Until the 19th century, homosexual activity was referred to as "unnatural, crimes against nature", sodomy or buggery and was punishable by law, sometimes by death.
As people became more interested in discovering the causes of homosexuality, medicine and psychiatry began competing with the law and religion for jurisdiction. In the beginning of the 19th century, people began studying homosexuality scientifically. At this time, most theories regarded homosexuality as a disease, which had a great influence on how it was viewed culturally. There was a paradigm shift in the mid 20th century in psychiatric science in regards to theories of homosexuality. Psychiatrists began to believe homosexuality could be cured through therapy and freedom of self, and other theories about the genetic and hormonal origin of homosexuality were becoming accepted. There were variations of how homosexuality was viewed as pathological. Some early psychiatrists such as Sigmund Freud and Havelock Ellis adopted more tolerant stances on homosexuality. Freud and Ellis believed that homosexuality was not normal, but was "unavoidable" for some people. Alfred Kinsey's research and publications about homosexuality began the social and cultural shift away from viewing homosexuality as an abnormal condition. These shifting viewpoints in the psychological studies of homosexuality are evident in its placement in the first version of the Diagnostic Statistical Manual (DSM) in 1952, and subsequent change in 1973, in which the diagnosis of ego-dystonic homosexuality replaced the DSM-II category of "sexual orientation disturbance". However, it was not until 1987 in DSM-III-R that it was entirely dropped as a mental disorder.