But once you get interested in schizophrenia, it doesn't take long for the whole edifice to look a bit crumbly. For almost as long as schizophrenia has been around there has been contention about it as an entity. This contention is not just an expression of "phenomenologic relativism" (Lieberman's angry charge), it is a respectable doubt about whether the construct of schizophrenia is a valid object for scientific study. It has been articulated most elegantly by Richard Bentall and Mary Boyle, who both conclude that schizophrenia is not a valid construct. When you try to find examples of people refuting their position, it's hard to come up with much of substance. Thus, a chapter on the construct of schizophrenia in Daniel Weinberger's big textbook on schizophrenia says this:
The diagnostic criteria currently used (ICD - 10 and DSM - IV - TR) can be considered provisional and arbitrary constructs with some face validity that meet the objective of facilitating international communication and research. (p.9)Meanwhile, in their Very Short Introduction to Schizophrenia, Chris Frith and Eve Johnstone acknowledge Mary Boyle's long and detailed book, but they dismiss it by saying simply "we are not convinced" (this comment appears in a Further Reading section at the back of their book).
Given all the articulate doubt, and its less than convincing refutation, why has the schizophrenia label survived? When this question has been asked by critically minded scholars, the answer has tended to be "money and professional esteem". David Pilgrim endorses a version of this argument in an essay in "Reconstructing Schizophrenia", and in "Madness in Civilization", Andrew Scull points out that "chronic conditions are chronically profitable" (p.393).
There can be no doubt that the financial and professional interests of psychiatry and pharmaceutical companies play a role in the survival of schizophrenia, but this explanation cannot be the whole story. Both motivations played a role in the brief flurry of interest in Paediatric Bipolar Disorder (an ugly controversy documented well in multiple posts by One Boring Old Man), but the APA, cogent of its many problems, ultimately moved to stop that diagnosis getting into DSM-5. That is not proof that the APA's mechanisms for self regulation are good enough, but it does suggest the need for another ingredient in order for a disorder to become as successful as schizophrenia.
What is missing in the economic account of schizophrenia's survival is the fact that, validity concerns notwithstanding, there is a way in which the diagnosis is very convincing; on the face of it many people who meet criteria for schizophrenia seem to be seriously unwell and many of them will testify to that fact. This is something that schizophrenia's many critics frequently seem to miss. It is largely (though not entirely) missing from the BPS's Understanding Psychosis document, and it is missing from the writing of Bentall, Boyle, and others, who tend to view their work as a foundation for moving away from an "illness model" of what they refer to as "psychological distress".
In fact, even the ultimate collapse of schizophrenia would not be tantamount to evidence that there are no illnesses in the space the diagnosis used to occupy. In a staunchly critical book "Schizophrenia is a Misdiagnosis", the psychiatrist C.Raymond Lake argues that schizophrenia cannot be distinguished from severe psychotic mood disorders, and also provides a long list of disorders which can get diagnosed as schizophrenia (see below).
Perhaps then the persistence of schizophrenia can partly be attributed to a case of a divided opposition. All of schizophrenia's critics can be seen as wanting to carve away chunks from the existing construct by placing people into alternative categories. For some these chunks are "psycho-social distress" (i.e. not ill at all), for others they should go into more precise medical categories (i.e. ill with something doctors actually understand). To some extent these players in the debate speak at cross purposes; they might even be construed as competing over territory:
Schizophrenia as shrinking territory.
Schizophrenia's medical critics believe that progress will come as more and more people currently in the "bucket" of schizophrenia are given a correct medical or psychiatric diagnosis (as the yellow section expands). This quieter territory expansion is constantly ongoing, with new "subgroups" of schizophrenia emerging periodically, associated with specific physiological characteristics (a very recent example is here). When these subgroups are sufficiently well understood they raise an interesting problem; are they still a form of schizophrenia, or (given that the DSM definition of schizophrenia has an exclusion clause saying that symptoms must not be due to the direct physiological effects of a [...] general medical condition.) have they become something else?
It is this ongoing uncertainty which surely accounts for the continued plausibility of schizophrenia in the psychiatric and public imaginations. Yes there are many people who fall in the purple and yellow overlaps of my venn diagram, but there are others (how many?) who currently do not. The hypothetical construct schizophrenia is a testament to the suspicion that, when everything tumbles out, there will be a well understood bio-psycho-social process giving rise to the symptoms in DSM-5. Should that process be sufficiently well understood, it might be what we end up giving the name "schizophrenia" 100 years from now.
Alternatively, the purple and yellow sections may keep expanding, finally squeezing schizophrenia out of the picture altogether. Only an omniscient being can currently say how much of the middle circle will be left in the end. For the time being no amount of political activity seems sufficient to quell people's suspicion that when psychiatry talks about schizophrenia, it is talking about something worth naming.