Urinary phenylacetic acid in panic disorder with and without depression.

Phenylacetic acid (PAA) excretion was measured in 39 patients who met criteria for panic disorder; 9 of these also had major depression, and 30 did not. Patients with panic and depression excreted 66 +/- 23 mg/day of PAA, an amount significantly lower than in normal controls; patients with panic disorder but without depression excreted 104 +/- 23 mg/day of PAA (not significantly lower than controls). The results support previous studies indicating that PAA excretion is a marker for depressive disorder.