Background: Two major biomarkers of suicidal behaviour; low 5-hydroxyindoleacetic acid (5-HIAA) in the cerebrospinal fluid (CSF) and non-suppression in the dexamethasone suppression test (DST) have evidence for predictive power for suicide in mood disorders. Previous suicide attempt is the most robust clinical risk factor.
Purpose of study: To study the interrelationship of suicide risk factors: low CSF 5-HIAA and the DST non-suppression in mood disorder patients with and without an index suicide attempt.
Methods: Fifty-eight hospitalised mood disorder patients (twenty-five with an index suicide attempt), who were not receiving any treatment with antidepressants, underwent lumbar puncture and DST. Plasma cortisol levels were determined from blood samples drawn the following day at 8:00 a.m., 4:00 p.m. and 11:00 p.m. and analysed in relation to CSF 5-HIAA.
Results: In the sample as a whole, the serum cortisol level at 4:00 p.m. showed a significant positive correlation to CSF 5-HIAA (r=0.3, p<0.02). In the patients with an index suicide attempt, the serum cortisol at 4.00 p.m. correlated positively with CSF 5-HIAA (r=0.65, p<0.0006), but not in the non-attempters (NS).
Conclusion: The positive correlation means that low CSF 5-HIAA and DST non-suppression are relatively independent biomarkers of suicide risk in suicide attempters. The interrelation of the two systems seems to be different in suicide attempters compared to depressed inpatients without suicide attempt.