Two
biomarkers of suicide risk; non-suppression in the
dexamethasone suppression test (DST) and low 5-hydroxyindoleacetic
acid (5-HIAA) in the cerebrospinal fluid (CSF) have been reported to be predictors of suicide in
mood disorders. The interrelation of the two systems seems to be different in suicide attempters compared with depressed inpatients who have not made a suicide attempt, indicating that the two
biomarkers may be seen as independent. This investigation examined the interrelation of low CSF
5-HIAA and DST non-suppression in suicide victims with
mood disorder. Fifty-eight
mood disorder inpatients not receiving any treatment with
antidepressants underwent lumbar puncture and the DST. Plasma
cortisol levels at 8:00 a.m., 4:00 p.m. and 11:00 p.m. were analysed in relation to CSF
5-HIAA. All patients were followed up for causes of death and suicides were verified with death certificates. During follow-up (mean 21 years), 11 (19%) patients had committed suicide. In male suicide victims (n=6), the serum
cortisol level at 4:00 p.m. showed a significant positive correlation with CSF
5-HIAA. Low CSF
5-HIAA predicted all early suicides (within 1 year), whereas all males who committed suicide after 1 year were DST non-suppressors. In female suicide victims (n=5), the post-DST serum
cortisol did not correlate with CSF
5-HIAA. Low CSF
5-HIAA and DST non-suppression are orthogonal
biologic risk factors for suicide in male
mood disorder inpatients. CSF
5-HIAA is associated with short-term suicide risk; dysregulation of the hypothalamic-pituitary-adrenal axis seems to be a long-term suicide predictor.