The orexins are recently discovered hypothalamic peptides involved in the regulation of sleep, appetite, & state of arousal. The relationship between cerebrospinal fluid orexin & specific psychiatric symptoms in 101 patients who had attempted suicide was investigated. There were significant & negative correlations between cerebrospinal fluid orexin & the symptoms lassitude & slowness of movement as well as the ratings of global illness. The lower the orexin levels, the higher were ratings of overall ilnness, as observed by a psychiatric specialist. (28 refs.)