See D.L. Rosenhan; On Being Sane in Insane Places. Published in Science (Jan 19,1973). still available online. Rosenhan (a psychologist) and 7 others (some in the field of mental health, all of them otherwise sane) did an initial test of the ability of MH professionals to recognize sanity. They each went to different psychiatric hospitals and claimed they had been hearing voices. They were admitted, given a psychiatric label and remained (from 7 to 52 days). The other patients recognized that they were sane. The doctors and hospital staff didn’t and the 8 were released with a diagnosis of mental illness. When the report was published in Science in 1973 it was denounced by psychiatrists as a hoax. No one dared repeat the study to prove or disprove it for over 40 years (probably fearing they would be blackballed professionally). Rosenhan quietly stood by this brief test of the mental “health” system’s ability to recognize sanity for the rest of his life–but he got into another, related field of law relating to mental illness and taught at Stanford in California.