In 1973, a Stanford psychology professor sent eight healthy people into twelve psychiatric hospitals with instructions to feign a single hallucinatory symptom, then act normally, in an experiment that reshaped the entire field of American psychiatry and that turned out, almost fifty years later, to have been hiding something nobody had thought to look for

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In the late 1960s and early 1970s, American psychiatry was in the middle of a public credibility crisis. The diagnostic manual the profession depended on, the DSM-II, had been published in 1968 and was widely understood, even within the profession, to be unreliable. Different psychiatrists examining the same patient frequently produced different diagnoses. The same patient examined at different times could be diagnosed with different conditions. Critics inside and outside the profession argued that psychiatric diagnosis was essentially a matter of clinical opinion dressed up in the language of medicine, and that what the field called mental illness was as much a social construct as a clinical reality.

The criticism was not new. The novelist Ken Kesey had published One Flew Over the Cuckoo’s Nest in 1962. The Scottish psychiatrist R. D. Laing had been arguing for nearly a decade that schizophrenia might be a rational response to an irrational society. The Hungarian-American psychiatrist Thomas Szasz had argued in 1961 that mental illness itself was, in most cases, a metaphor rather than a literal disease. The anti-psychiatry movement was substantial, vocal, and influential. What it lacked was a single piece of empirical evidence that could decisively demonstrate whether the criticisms were correct.

In January 1973, a piece of such evidence appeared in the journal Science. It was nine pages long. Its author was a Stanford professor of psychology and law named David Rosenhan. Its title was "On Being Sane in Insane Places."

It would, in the years that followed, become one of the most cited critiques of psychiatric diagnosis in the history of the field.

The eight pseudopatients

The study Rosenhan described in his 1973 paper was, on the face of it, a straightforward field experiment. He had recruited eight people, including himself, who had no history of psychiatric illness and no current symptoms of any psychiatric disorder. Three of the pseudopatients were women. Five were men. Their occupations included a psychology graduate student, a paediatrician, a psychiatrist, a painter, a housewife, and Rosenhan himself. None of them had any direct experience of being a psychiatric patient.

Rosenhan instructed each of them to present themselves at the admissions desk of a psychiatric hospital and report a single symptom. They were to say that they had been hearing a voice. The voice, they were to report, was unfamiliar to them, the same sex as themselves, and seemed to be saying single words, mostly "empty," "hollow," and "thud." The pseudopatients were instructed to give their real life histories in every other respect, with only the names of close family members changed to protect their privacy. They were to describe their actual marriages, their actual employment, their actual childhood relationships. The single symptom of the unfamiliar voice was the only fabrication they were permitted.

From the moment they were admitted to a psychiatric ward, they were to behave entirely normally. They were to stop reporting the voice. They were to take whatever medications they were prescribed and surreptitiously dispose of them. They were to engage with the staff and other patients in the ordinary way, comply with hospital procedures, and attempt to secure their own release by demonstrating that they were not, in fact, mentally ill.

The pseudopatients did not know how long they would be hospitalised. They did not know what diagnoses they would receive. They did not know how the staff would interpret their behaviour. They did not, in some cases, know whether the experiment would be considered a success or a failure. They had been told only that Rosenhan would secure their release if they were unable to secure it themselves, and that the experiment was investigating whether psychiatric hospitals could reliably distinguish people who were genuinely ill from people who were not.

This video goes into more detail about the case – click here to watch it.

Twelve hospitals, five states, two coasts

The twelve hospitals to which the pseudopatients presented themselves were distributed across five states on the East and West Coasts of the United States. They included old, underfunded state hospitals and modern, well-funded research hospitals. Some were affiliated with prestigious universities. Some had reputations for poor quality of care. Some were considered exemplary by the standards of contemporary American psychiatry. The selection had been designed to test whether the experimental results would depend on the institution...