Xanthurenic acid flow in 24-hour urine following L-tryptophan loading in depressive patients.

The xanthurenic acid (XA) flow in 24-hour urine following L-tryptophan loading was determined in a control group and in depressive patients divided into two DSM-III categories: minor depression (dysthymic disorder, atypical depression, adaptation disorder with depressive mood), and major depression. The XA flow is not significantly (p = 0.15) different in these categories of depression and in the control group. The number of patients with an abnormal XA flow (cut-off value greater than or equal to 106.8 mu mol/24 hours) is not significantly different among these groups (p = 0.40). The XA flow is therefore not relevant whether for depression or major depression. The XA flow in 24-hour urine following L-tryptophan loading decreases with age (p = 0.006) and increases with the 24-hour urinary output (p = 0.02). Women excrete significantly more XA (p = 0.02) than men. One must take age, 24-hour urinary output and sex into account for the interpretation of the XA data.