Neuromuscular abnormalities in the major mental illnesses. I. Serum enzyme studies.

Eighty-eight of 187 (47.1%) psychotic patients had increased serum creatine phosphokinase (CPK) activity at admission. By the time of discharge, 75.9% had had an increased serum CPK activity. There was no significant difference between various groups of types of psychoses in the incidence of increased serum CPK activity. In 25% of the patients with increased serum CPK levels, the peak increase was equal to or greater than five times the upper limit of normal. Only the skeletal muscle isozyme of CPK was present in serum. The incidence of increased serum CPK activity at admission is significantly greater for those patients whose gross psychotic symptoms began 1 to 7 days prior to admission than for those whose symptoms began 8 or more days prior to admission. Some types of psychopathology were more intense or more frequently present in those patients with increased serum CPK activity at admission. Moreover, patients with increased serum CPK activity at any time during hospitalization had significantly greater mean ratings of some types of psychopathology, longer mean hospitalization and required higher doses of medication than did patients who never had such increases. Serum CPK levels were correlated with particular types of behavior for many psychotic patients. "Baseline" mean serum CPK activity of psychotic patients with increased serum CPK levels at some time during hospitalization was significantly greater than that of psychotic patients who never had increases in the hospital. One hundred and three of 337 (30.6%) first-degree relatives of psychotic patients also had slightly increased serum CPK activity. A significantly greater proportion of the relatives with slight elevation were related to patients who had elevated serum CPK activity. Many of the characteristics of increased serum CPK levels in patients with various types of major mental illnesses are similar to each other and to increases present in patients with a variety of acute brain diseases. This obviously does not mean that all these diseases have a common cause. They may, however, share a common mechanism producing increased efflux of CPK from skeletal muscle or decreased clearance of CPK from serum. Determination of serum CPK activity in newly admitted psychiatric patients may help distinguish psychotic from nonpsychotic patients, but the number of false-negatives and -positives will be considerable. The most important values of serum CPK determinations in psychotic patients may be to stimulate further investigations of the neuromuscular system.