Serum Melatonin at Admission and Discharge in Schizophrenia: A Prospective Longitudinal Controlled Study

Schizophrenia is associated with circadian and neuroendocrine disturbances, but whether circulating melatonin changes with acute clinical state remains uncertain. This prospective longitudinal controlled study measured serum melatonin at 12:00 and 00:00 in 43 hospitalized patients after admission and before discharge, and during one session in 42 healthy controls. Psychopathology was assessed using the Positive and Negative Syndrome Scale (PANSS). Nonparametric comparisons used family-specific Holm adjustment; exploratory correlations used false-discovery-rate control. In comparisons without covariate adjustment, midday concentrations were higher in patients at admission and discharge (Holm p = 0.013 and 0.007), but the differences did not remain significant after Holm correction in exploratory models adjusted for BMI, age, and sex (29 patients and 40 controls). Median within-patient changes were -0.14 pg/mL at 12:00 (95% CI -0.27 to 0.74) and 0.00 pg./mL at 00:00 (95% CI -2.00 to 6.35); both Holm p = 1.000. Total PANSS decreased by a median of 14 points among 24 complete pairs. No change-PANSS correlation survived multiplicity correction. Two daily samples demonstrate a midday-midnight concentration difference but cannot characterize circadian phase, amplitude, or total secretion. No short-term melatonin change was detected during hospitalization; this does not establish equivalence or confirm or exclude trait-biomarker status. State-marker utility remains uncertain, and patient-control differences may reflect medication, smoking, or confounding by assay plate.