Orexin and psychiatric symptoms in suicide attempters

BackgroundThe orexins (hypocretins) are recently discovered hypothalamic peptides that are involved in the regulation of sleep, appetite and state of arousal. In the present study, we investigated the relationship between cerebrospinal fluid (CSF) orexin and specific psychiatric symptoms in suicidal patients.MethodsA total of 101 patients were enrolled in the study shortly after a suicide attempt. All patients underwent a lumbar puncture after a wash-out period during which they did not receive any antipsychotic or antidepressive medication. Structured interviews were performed using the Comprehensive Psychopathological Rating Scale (CPRS). CSF-orexin-A was measured and correlated with ratings of psychiatric symptoms.ResultsThere were significant and negative correlations between CSF-orexin and the symptoms lassitude (difficulty to initiate activities) and slowness of movement, as well as the ratings of global illness (p < 0.005 for all three items, Spearman's rho).LimitationsCorrelation analysis is an indirect method of investigation and does not demonstrate causal relationships.ConclusionLow CSF-orexin levels are related to pronounced symptoms of inertia and reduced motor activity in suicidal patients. Interestingly, the lower the orexin levels, the higher were ratings of overall illness, as observed by a specialist in psychiatry. Our results suggest that reduced orexin levels are involved in the etiology of specific psychiatric symptoms.