Diagnostic classifications in depression and somatization should include biomarkers, such as disorders in the tryptophan catabolite (TRYCAT) pathway
Psychiatry Research, 05/31/2012

Maes M et al. – Cluster analysis has generated a “pathway phenotype”, i.e. aberrations in the tryptophan catabolite pathway, which are associated with somatization rather than with depression.

• Plasma TRP, the kynurenine (KY)/TRP and KY/kynurenic acid (KA) ratios were measured in 36 patients with somatization, 35 depressed and 38 depressed+somatization patients and 22 controls.
• Using pattern recognition methods, the diagnosis comorbid depression+somatization could not be validated, while there was an important overlap between depression and somatization, which form one continuum.

• Cluster analysis detected
  • A control cluster.
  • A cluster with lower tryptophan, and higher KY/TRP and KY/KA ratios and somatization scores.
  • A cluster with increased depression but lower KY/TRP values.
  • The differences between both patient clusters were quantitative and not qualitative.