Homosexuality is a psychological disorder requiring treatment.

In the autumn of 1971, a group of gay activists led by Frank Kameny stood up from the audience during a session at the American Psychiatric Association's annual meeting in Washington, D.C., and seized the microphone. Kameny had been fighting the classification of homosexuality as a mental disorder for over a decade, since his discharge from federal employment in 1957 for being gay. He had filed what may have been the first civil rights lawsuit challenging government antigay discrimination, petitioned the Civil Service Commission, and corresponded with leading psychiatrists. He had, in more than one letter, accused the American Psychiatric Association of presenting a pathological fiction as scientific fact.

The 1971 disruption was theatrical, but the question it forced onto psychiatry's agenda was scientific. Was the classification of homosexuality as a mental disorder based on evidence, or on cultural assumption? The DSM-II's entry was frank about its empirical basis: homosexuality was included because it appeared regularly in clinical populations. But appearing in clinical populations is not evidence of pathology. People who seek psychiatric care are a self-selected group, and in a society where homosexuality was stigmatized, criminalized in every state, and grounds for dismissal from employment and military service, a homosexual person who sought therapy was often doing so because of the consequences of stigma, not because the orientation itself caused disorder.

This was the argument Evelyn Hooker had made with data in 1957, in research showing that trained clinicians could not distinguish homosexual from heterosexual men on standard psychological tests when working from non-clinical populations. It was the argument that psychiatrist Robert Spitzer, as he engaged with gay activists and reviewed the accumulating literature, came to find persuasive.

In 1972, a gay psychiatrist named John Fryer appeared at the APA's annual meeting in Dallas, masked and disguised, under the pseudonym "Dr. Henry Anonymous." Fryer described his experience of practicing psychiatry while closeted, treating gay patients with a model he personally knew to be false, and existing within a profession that classified him as disordered. The session was recorded. It was later said to have shifted the mood of the meeting more than any formal paper.

Over the following year, Spitzer organized hearings within the APA's Committee on Nomenclature and Statistics, reviewing the empirical literature on homosexuality's relationship to psychological functioning. The evidence consistently pointed the same direction: homosexuality did not meet the APA's own criteria for a mental disorder, which required that a condition cause subjective distress or generalized impairment in social functioning. Many gay people reported neither. The distress that clinical patients reported was better explained by social stigma and its consequences, employment discrimination, family rejection, criminalization, than by any intrinsic feature of same-sex attraction.

In December 1973, the board voted. Homosexuality was removed from the DSM. A new category, "Sexual Orientation Disturbance," was added for individuals distressed by their orientation, an acknowledgment that conflict with social norms could cause genuine suffering, while removing the implication that the orientation itself was pathological. A member referendum in 1974 upheld the decision, 5,854 to 3,810.

The clinical practices that had accumulated under the old classification did not end immediately. Conversion therapy, the attempt to change sexual orientation through psychological or behavioral techniques, continued to be practiced through the 1980s and into the 2000s, with major professional organizations repeatedly finding no evidence that it worked and substantial evidence that it caused harm including depression, anxiety, and suicidality. The APA issued formal statements against it in 1997 and 2009.

But the formal nosological change of 1973 opened the door: a disorder that no longer existed in the diagnostic manual could no longer be treated with clinical authority. The vote had been five years in the making from Kameny's first disruption of a psychiatric conference, and decades in the making from Hooker's blind study that professionals had found it inconvenient to hear.