Biological predictors of suicidality in schizophrenia.

The objective of this study was to determine whether polysomnographic rapid eye movement (REM) sleep abnormalities and cortisol response to the dexamethasone suppression test (DST) differentiate between schizophrenic patients with and without a history of suicidal behaviour. We assessed a sample of 96 schizophrenic in-patients at the end of a 2-week medication-free period with the DST, polysomnography, and an extensive clinical assessment battery. Patients exhibiting suicidal behaviour were significantly more likely to have increased total REM time and increased total REM activity. We found no significant relationship between suicidal behaviour and DST non-suppression. This study confirms a previous finding suggesting an association between REM sleep abnormalities and suicidal behaviour in schizophrenia. It is postulated that this observed association may be related to serotonergic dysfunction in schizophrenia.