Serum melatonin levels in schizophrenic and schizoaffective hospitalized patients.

Conflicting results on changes of the diurnal melatonin rhythms of patients with affective disorders have been reported in the literature. The heterogeneous data may derive from the great discrepancy in the diagnostic criteria of different authors. A study of 12 schizoaffective and chronic schizophrenic psychotic patients found a constant pattern of an obliterated nocturnal melatonin rise only in the latter group. The presence or absence of the nocturnal melatonin rise was determined in drug-free hospitalized patients and remained unchanged despite 2 months of drug treatment including large doses of neuroleptics. This finding, when confirmed in a larger number of patients, could possibly serve as a marker for the type of mental disorder, drug to be applied and response expected.