Boundaries of schizophrenia

Several lines of evidence suggest that rather than representing homogenous and distinct syndromes, schizotypal and schizophreniform disorders are related to or represent milder forms of schizophrenia. In addition to the ongoing debate as to divisions between schizophrenia and disorders of the schizophrenic spectrum, it has been suggested that some affective and anxiety disorders might also overlap phenomenologically with schizophrenia. There have long been questions as to the relationship of schizophrenia to some affective syndromes, particularly bipolar and schizoaffective disorders. Despite similarities between schizophrenia and bipolar disorder however, significant differences extend across suggested etiologies, phenomenology, and pathophysiology and is reflected in distinct epidemiological pedigrees. Schizoaffective disorder, in contrast, appears to be composed of distinct syndromes linked to either schizophrenia or bipolar disorder. Obsessive-compulsive disorder also seems to involve pathology in many of the same regions as schizophrenia, reflected by a high incidence of co-morbidity. Other evidence however, suggests that obsessive-compulsive disorder does not represent a forme fruste of schizophrenia in the same manner as schizotypal and schizophreniform disorders. These findings suggest that while schizophrenia is clearly a heterogeneous syndrome that may be comprised of many distinct pathological entities and in turn comprises disorders across a spectrum of severity it may be usefully distinguished from affective disorders such as bipolar disorder, and anxiety disorders such as obsessive-compulsive disorder with which it shares many clinical characteristics.