Excerpts from SCHIZOPHRENIA VS MOOD DISORDER: A PUZZLE SOLVED, by Godfrey Pearlson, M.D. 1, Smooth Sailing, Fall 1996, 1-2

Clinicians have always struggled to distinguish among various mental disorders. These distinctions are important because they can predict which patients will respond to which treatments and identify which individuals will do better than others....

One hundred years ago, the German psychiatrist Emil Kraepelin...made the first clear distinction between...schizophrenia and manic depression/mood disorders....

...Some eminent present-day psychiatrists, however, ...still claim that schizophrenia and bipolar disorder are only extremes or represent different aspects of the same disease....

...Because we increasingly recognize mental illnesses as being brain diseases, one relevant question we can ask is, "When people with schizophrenia or mood disorders are compared with healthy volunteers (controls), are the observed brain changes the same or different for the two illnesses?"

Our research group recently tried to answer this question in a series of patients clearly diagnosed with either manic depression or schizophrenia....We used magnetic resonance imaging (MRI) to measure brain structures believed to be involved in the normal functioning of moods, emotions, and perceptions.

These structures included the amygdala, an almond-shaped nugget of brain tissue buried deep in the temporal lobe; the entorhinal cortex, a section of primitive "smell brain" that helps map events in the outside world into our consciousness; and asymmetries, areas of the brain that are normally bigger on one side than on the other (for example, in right-handed people, brain areas concerned with language are significantly bigger on the left than on the right side of the brain). These measurements were made from MRI brain scans of 27 people with mood disorders, 42 people with schizophrenia, and 58 healthy controls with no personal or family histories of mental illness.

Somewhat to our surprise, the results were fairly clear-cut. Compared with the healthy controls, schizophrenic patients had greatly shrunken entorhinal cortexes and striking reversals of some key brain asymmetries, but in manic-depressive patients these structures looked just like they did in the healthy controls. The amygdala was moderately shrunken but of equal size on the right and left sides of the brain in schizophrenic patients. In mood disorder patients, however, the amygdala was unchanged on the right side but very significantly shrunken on the left.

So, what can we carry away from this research? The observation that in both patient groups, brain structures differed in size from the same structures in healthy controls helps confirm our basic idea that both mood disorders and schizophrenia are brain diseases. However, the sizes of the brain structures in the two patient groups differed from the normal sizes in different ways, strongly suggesting that mood disorders and schizophrenia are distinct diseases, associated with distinct patterns of brain changes.

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1 Professor, Department of Psychiatry, Johns Hopkins University School of Medicine

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