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.

Transcultural psychiatry studies whatever pertains to the field of psychiatry in relation to cultural differences. The variable in these studies is the culture. We can study whether a given culture confers a special type of symptomatology to schizophrenia. We can attempt to determine whether a given culture enhances the occurrence of some syndromes, related to schizophrenia, but not generally included in the schizophrenic category.

We shall now study schizophrenia from the point of view of its progression, meaning progression toward regression.