The clinical significance of an elevated excretion of xanthurenic acid in psychiatric patients.

This study investigations whether the synthesis of nicotinamide out of L-tryptophan is disordered in depression or in anxiety. To this end the excretion of xanthurenic acid (XA) in 24 hours urine was measured after administration of an oral loading dose of 5 grams L-tryptophan. The subjects were depressive, anxious, and alcoholic patients, while other psychiatric patients, served as control group. Anxiety and not depression is the clinical correlate of an elevated excretion of XA. Liver disorder and vitamin B-6 deficiency have to be excluded. A psychiatric control group is necessary.