CSF biomarkers in suicide attempters - a principal component analysis

Objective: The objective of the present study was to identify biological patterns (factors) among 20 cerebrospinal fluid (CSF) biomarkers in suicide attempters and subsequently analyse their association with suicidal behaviour. Method: We measured kynurenic acid, orexin, homovanillic acid (HVA), 5-hydroxyindoleacetic acid (5-HIAA), 3-methoxy-4-hydroxyphenylglycol, chemokines, matrix metalloproteases and cytokines in the CSF of 124 drug-free suicide attempters. Patients were evaluated for suicidality and psychiatric symptoms using well-defined psychiatric rating scales and followed-up regarding future suicide. We used principal component analysis to identify factors among the biological substances. Results: Four factors were extracted from the 20 biomarkers, explaining 52.4% of the total variance. Factors 1 and 2 were characterized by high loadings of chemokines and cytokines respectively. They were both associated with severe depressive symptoms. Factor 2 was also associated with a high suicidal intent. Factor 4 was characterized by strong loadings of the monoamine metabolites 5-HIAA and HVA, as well as orexin and interleukin-6. High scores on this factor were found in patients who performed a violent suicide attempt and in patients who subsequently completed suicide. Conclusion: Our results suggest that specific combinations of CSF biomarkers may discriminate between types of suicidal behaviour and indicate increased risk for future suicide.