The American Psychiatric Association position paper (PDF format) on reparative or conversion therapies
The potential risks of "reparative therapy" are great, including depression, anxiety and self-destructive behavior, since therapist alignment with societal prejudices against homosexuality may reinforce self-hatred already experienced by the patient. Many patients who have undergone "reparative therapy" relate that they were inaccurately told that homosexuals are lonely, unhappy individuals who never achieve acceptance or satisfaction. The possibility that the person might achieve happiness and satisfying interpersonal relationships as a gay man or lesbian is not presented, nor are alternative approaches to dealing with the effects of societal stigmatization discussed. Therefore, the American Psychiatric Association opposes any psychiatric treatment, such as "reparative" or "conversion" therapy which is based upon the assumption that homosexuality per se is a mental disorder or based upon a prior assumption that the patient should change his/her homosexual orientation.
"Reparative therapy," also known as conversion therapy, is a term that is used to describe treatment attempts to change a person from a homosexual orientation to a heterosexual orientation. There is no published scientific evidence supporting the efficacy of "reparative therapy" as a treatment to change ones sexual orientation. It is not described in the scientific literature, nor is it mentioned in the APA’s latest comprehensive Task Force Report, Treatments of Psychiatric Disorders (1989).
There are a few reports in the literature of efforts to use psychotherapeutic and counseling techniques to treat persons troubled by their homosexuality who desire to become heterosexual; however, results have not been conclusive, nor have they been replicated. There is no evidence that any treatment can change a homosexual person’s deep seated sexual feelings for others of the same sex.
Clinical experience suggests that any person who seeks conversion therapy may be doing so because of social bias that has resulted in internalized homophobia, and that gay men and lesbians who have accepted their sexual orientation positively are better adjusted than those who have not done so.