I've been meaning to post up a link to this for a while: it's the published report of an experiment which took place in the early seventies, titled "On Being Sane In Insane Places."
To greatly summarize, a varied group of people who might be considered "normal" (in this context, that should be taken to mean having an absence of any psychiatric symptoms) agreed to become pseudopatients, such that they would each attempt to gain admission to psychiatric hospitals. The way they would go about this was agreed in advance, each one would go to a different hospital and complain of hearing a voice saying specific things.
None of the hospitals or their respective staff knew of the experiment, and each "patient" would not, apart from reporting the particular symptom in their initial appointment, otherwise attempt to behave abnormally or falsify any aspect of their life history.
Once admitted, each "patient" would have to aim towards being discharged by convincing the hospital staff that they were "sane."
Although not without its perceived flaws (some mention of which is made here), it makes for compelling and unsettling reading.
It raised questions about how "normal" behaviours become symptomized when a person is labelled and viewed in a specific context and environment. For example, as part of the experiment the "patients" wrote notes about their experiences whilst in hospital, and in one case this was taken to be a sign of pathology by the staff, noting it as being "writing behaviour" and hence giving the connotation that there was something obsessive about it.
There are numerous other examples of how the ordinary facts of a person's life, background and behaviour are distorted to fit the picture of mental illness now that they are hospitalized.
Interestingly (among many other adjectives that could be applied), none of the staff in any of the hospitals were able to identify the presence of any of these pseudopatients, although many of the other actual patients did cotton on to the fact that there was nothing wrong with them.
I may (or knowing me, I may not... or not for some time) post some observations loosely related to the above stemming from my own experience through work and also from a personal perspective.