Sleep-promoting action of the endogenous melatonin in schizophrenia compared to healthy controls

Objective. The aim of this study was to compare the endogenous melatonin sleep-promoting effect in schizophrenic patients to a sample of healthy controls. Methods. Thirty-four schizophrenia outpatients (SP) and 34 healthy subjects (HS) participated in this study. Wrist-actigraphy recordings and a sleep diary were used for sleep-wake cycle assessment. The quality and patterns of sleep were measured with the Pittsburgh Sleep Quality Index (PSQI) and the Positive and Negative Syndrome Scale (PANSS) was used for psychopathology assessment. To quantify and assess nocturnal melatonin profiles, saliva samples were collected for one night under dim light conditions (<50 lux) hourly from 20:00 h to 23:00 h. Results. Scores on PSQI were significantly higher in SP as compared to HS, indicating a worse quality of sleep. Patients sleep more at night, but have poorer sleep efficiency, than HS. Sleep latency and nighttime awakenings were significant higher in SP. Melatonin levels were negatively correlated with sleep latency, total sleep time and positively correlated with sleep efficiency in HS but not in SP. Conclusion. The results of the present study indicate that endogenous melatonin sleep-promoting action seems to be compromised in schizophrenia.