We have now come to the fourth, or last, stage of schizophrenia during which a new set of phenomena occurs. Some of the symptoms appear no longer as predominantly psychological but neurological. It seems as if the disorder has reached a level where psychology and neurology coalesce.

A summary of the progression of of schizophrenia from the first through fourth stages.

In the studies on the origins of schizophrenia, the constitutional, cardiovascular, endocrinological, and neuropathological researches have lost ground. On the other hand, the genetic, biochemical, and neurophysiological approaches have gained support.

A large number of researchers have carried out biochemical investigations of schizophrenia, pursuing the hypothesis that a biochemical or metabolic error is at the basis of the disorder.

We shall study separately gesture, action, and volition. By gesture we mean a motion of the body (or of parts of it) that expresses a special psychological state of the individual. By action we mean a purposeful or meaningful behavior, even if the purpose or meaning is not known to the subject. Volition is the process of choosing and of initiating, continuing, actualizing, interrupting, or terminating the chosen action. When we study volition, we refer to the process of choosing and putting into effect the action.

A visit to a large mental hospital would be sufficient to point out that the number of endocrine disorders is not much larger among schizophrenics than in the general population, and that an occasional endocrinopathy should be considered an accidental concomitant finding.

Almost every schizophrenic retreats from society to a mild, moderate, or pronounced degree. The patient seems to live in a shell, or in a world of his own, or behind what has been called an autistic barrier.

The schizophrenic process elicits psychosomatic attempts to integrate the highest cortical functions at a lower level. With comparatively few exceptions this attempt fails because the process engenders other self-perpetuating mechanisms that lead to regressions.

Of all the creative activities of the schizophrenic patient, painting is the one that has been studied the most, and we shall devote the bulk of this chapter to this subject.

Epidemiology is a science and methodology whose object is to determine whether there is an association between a rate of illness and the changing strength of an environmental factor. The characteristics that are studied in relation to the incidence of schizophrenia may be biological, psychological, sociological, or difficult to categorize.