Urinary MHPG, stress response, personality factors and somatosensory evoked potentials in normal subjects and patients with major affective disorders.

Stressful procedures are reported to increase urinary MHPG in both normal and depressed patients. Bipolar depressed patients are also shown to be especially pain tolerant in comparison to normals. In the present study, 12 depressed patients (6 bipolar and 6 unipolar patients) and 10 normal volunteers had average evoked potentials recorded for visual and painful electrical stimuli. MHPG urinary excretion was measured during this session and during an unstimulated resting session on the home ward. Male normal volunteers showed a significant increase in urinary MHPG under stress, while no MHPG increment was noted for the depressed group. Depth of depression, assessed by the Zung and Beck scales, was found to be correlated with the reduced urinary MHPG response to stress. Possible interpretations of the results are discussed.