From “Throughout History, Defining Schizophrenia Has Remained a Challenge [Timeline]” in Scientific American Mind:

Less than two hundred years ago, schizophrenia emerged from a tangle of mental disorders known simply as madness. Yet its diagnosis remains shrouded in ambiguity. Only now is the Diagnostics and Statistical Manual of Mental Disorders, psychiatrists’ primary guidebook, shedding the outdated, nineteenth-century descriptions that have characterized schizophrenia to this day. “There is substantial dissatisfaction with schizophrenia treated as a disease entity, it’s symptoms are like a fever—something is wrong but we don’t know what,” says William Carpenter, a psychiatrist at the University of Maryland and chair of the manual’s Psychotic Disorder Workgroup. Psychiatrists may discover that this disorder is not a single syndrome after all but a bundle of overlapping conditions.

Liah Greenfeld in “Madness in its Pure Form,” Chapter 3 in Mind, Modernity, Madness:

The root of the schizophrenic experience, from the earliest stages and throughout the episode, is the problem with the self, specifically the acting self: the dissolution of the will. The difference between the early, middle, acutely psychotic, and elaborate delusional stages for the patient consists in that, during the prodrome, the loss of the acting self is experienced indirectly, through changed experience of the outside world, becoming more and more direct through the middle stages, culminating in the sense of the loss of the mind (and both relationally-constituted self and the thinking self) in the stage of acute psychosis, and continuing in a partial restitution of identity and the thinking self, or the reconstruction of the self-in-the-world in the elaborate delusion. The structure of self-consciousness or the “I of Descartes” is involved at every stage in the disease process, but it changes its function from that of the thinking self to the one of the “eye of an external observer” and back, or, in other words, transforms from the part of the mind (individualized culture) to culture in general and back, confusing the levels of the mental and symbolic process. The different phases or stages of the illness, obviously, cannot be strictly separated but seamlessly flow and transmogrify one into another.

I would like to draw the reader’s attention to two points. 1. Seen in this light, as a mental, rather than a brain, disease, as the disorder of the mind, and therefore, a cultural phenomenon, schizophrenia appears to be of a piece. All of its symptoms (however contradictory they may seem when seen in other frameworks) can be accounted for by the loss of the acting self and related to each other through this overarching relationship to the impairment of the will. One is no longer forced to consider the extreme variability of abnormalities to be the single invariable characteristic of schizophrenia. There is, after all, an organizing principle which makes it possible to integrate all of its features into an understandable whole. 2. To arrive at this interpretation of schizophrenia and depict its underlying psychological structure, there was no need to step outside the theory of the healthy mind as outlined in Chapter 2, “The Mind as an Emergent Phenomenon.” No abnormality was interpreted ad hoc, proving the sufficiency of this theory. The analysis of schizophrenia, it is possible to claim, provides a strong support for its hypotheses regarding the structure of the mind.

It still remains to us, of course, to explain schizophrenia causally. As was stated in the Introduction, the explanation I propose is that modern society, based on the principles of nationalism, is profoundly anomic and, as such, makes the formation of identity (the relationally constituted self) problematic. Malformed identity, in turn, necessarily impairs the will. This hypothesis will be tested in two stages: first, through an examination of a well-documented contemporary case (the case of John Nash) and then, much more thoroughly, on the basis of comparative-historical analysis of the development of relevant aspects of the modern culture.