From New York Times:
Last fall, British television broadcast a reality program called “How Mad Are You?” The plot was simple: 10 volunteers lived together for a week in a castle in the Kent countryside and took part in a series of challenges. The twist was the lack of a prize. Five of the volunteers had a history of a serious mental illness, like obsessive compulsive disorder and bipolar disorder, and five did not. The challenges, meant to elicit latent symptoms, included mucking out a cowshed, performing stand-up comedy and taking psychological tests.
But the real test came at the end of the week.
Could a panel of experts — a psychiatrist, psychologist and a psychiatric nurse — tell them apart? They could not. After watching hours of videotape, the experts correctly identified only two of the five people with a history of mental illness. And they misidentified two of the healthy people as having a mental illness. The point was made: even trained professionals cannot reliably determine mental illness by appearances alone.