The boundaries of schizophrenia.

Evidence from a variety of domains including the phenomenologic, genetic, psychological, neuropsychological, psychophysiologic, neurochemical, imaging, outcome, and treatment response suggests that schizotypal personality disorder is related closely to chronic schizophrenia and that this disorder may be part of a continuum of schizophrenia-related disorders. Questions remain as to how the boundaries of schizophrenia should be defined. The commonalities across the schizophrenia spectrum as well as the differences between disorders on the spectrum need to be clarified further. A multidimensional approach to the pathogenesis of the schizophrenia-related disorders offers a beginning opportunity for such a clarification. The study of patients with schizotypal personality disorder suggest that a dimension of deficit-like or "negative" symptoms of asociality and interpersonal impairment may be associated with neuropsychological and psychophysiologic correlates of altered cortical, particularly frontal, function and raise the possibility in structural changes as reflected in increased ventricular size in frontal and third ventricle areas. On the other hand, the psychotic-like or "positive" symptoms seem to be more related to increases in dopaminergic activity that may be partially responsive to neuroleptic treatment. It is conceivable that these two dimensions may represent partially distinct but potentially interactive pathophysiologic processes that may converge and interact to result in chronic schizophrenia. In this way, the study of the boundaries of schizophrenia and the milder schizophrenia-related personality disorders may provide important clues as to the genetic and pathophysiology of chronic schizophrenia itself, as well as to illuminate a set of disorders that are clinically underrecognized but probably more prevalent than more severe forms of schizophrenia.