Diagnostic Boundaries between Bipolar Disorder and Schizophrenia: Implications for Pharmacologic Intervention*

Schizophrenia and bipolar disorder are distinguished primarily by course of illness and, consequently, share many similar symptoms cross-sectionally. This similarity presents a diagnostic challenge for clinicians, because accurate diagnosis often requires monitoring patients over time; however, treatment typically needs to be instituted quickly, further complicating this process. Conventional antipsychotics have been used to treat both conditions, but have proved to have little utility in the long-term management of bipolar disorder, and considerable side-effect liability for the long-term management of schizophrenia. The newer, second-generation antipsychotics have improved tolerability relative to the older agents and may provide thymoleptic properties, including affective relapse prevention, that expands our treatment armamentarium for newonset psychotic and affective disorders. (Adv Stud Med. 2003;3(8C):S792-S798) M uch of our current conceptual understanding of schizophrenia is based on observations made by the German psychiatrist Emil Kraepelin, who in 1896 described a group of psychotic patients who developed impaired cognition in their 20s or 30s, typically ending in poor outcome. Kraepelin proposed the separation of this syndrome, dementia praecox, from manic-depressive insanity, which shared many common features, primarily based on differences in the course of illness. Whereas he characterized dementia praecox (later reconceptualized and renamed schizophrenia) as a chronic, deteriorative disease, manic-depressive insanity (later renamed and reconceptualized as bipolar disorder) featured an episodic course and more favorable outcomes. Despite Kraepelin’s historic definition of and differentiation between 2 distinct psychotic disorders, considerable overlap between them persists more than 100 years later. The psychopathology of schizophrenia is usually described in terms of 3 somewhat independent symptom clusters: positive, negative, and disorganized. Positive symptoms include psychotic symptoms, such as delusions and hallucinations. Negative symptoms include withdrawal, impoverished emotional state, motivational difficulties, lack of energy, affective flattening, loss of spontaneity, and lack of initiative. Disorganization as a syndrome of schizophrenia includes incoherence, illogicality, loose associations, inappropriate affect, and poverty of thought content. Many of these symptoms also occur in bipolar disorder. Depression and anxiety are commonly associated with bipolar disorder, and are also common in schizoPROCEEDINGS