The aim of this research is to study whether serum melatonin level is related with positive psychopathology in a sample of paranoid schizophrenia patients.

32 acutely paranoid schizophrenia patients admitted to the psychiatric ward of the University Hospital of the Canary Islands took part in the study. All patients met DSM-IV criteria for paranoid schizophrenia. 22 were males and 9 females. The mean age was 36.7 ± 10.3 (standard deviation). Blood was sampled by venipuncture at 12:00 and 24:00 hours after having rested in bed one hour. This was done to avoid the body postural effect on melatonin levels. Blood extractions were carried out during the first 48 hours after admission. Psychopathology was assessed by the positive subscale of the Positive and Negative Syndrome Scale (PANSS). Melatonin serum levels were measured by ELISA techniques. Pearson correlations between melatonin serum levels and PANSS positive scores at 24:00 and 12:00 hours at admission and discharge were carried out.

The only significant correlation, with a positive sign, was the item Conceptual Disorganisation (P2) with serum melatonin at 24:00 h (r = 0.355, p < 0.046).

Serum melatonin levels may be used as a biological marker of conceptual disorganisation in paranoid schizophrenia inpatients.

This study was partly supported by a grant (PI: 08/115) of the Fundacion Canaria de Investigacion y Salud (FUNCIS).