CSF biomarkers in suicide attempters--a principal component analysis

Lindqvist D, Janelidze S, Erhardt S, Träskman‐Bendz L, Engström G, Brundin L. 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.