The 3 methoxy-4-hydroxyphenylglycol excretion (MHPG flow) and the creatinine excretion in 24 h urine, are measured in depressive inpatients, subdivided according to the DSM-III as minor depression (309.00, 300.40; 296.82), major depression without melancholia (296.22; 296.32), with melancholia (296.23; 296.33) and with psychotic features (296.24; 296.34). The no-depressive study group is stratified over the several DSM-III subcategories, with exclusion of the organic mental disorders, the substance use disorders and the (hypo)manic disorders. The effect of 24 h urinary output, creatinine flow, age and sex on the MHPG flow are controlled by analysis of covariance.

The MHPG flow is not significantly different between the depressive and non-depressive study groups. Within the full depressive sample, patients with melancholia show a significantly (p < 0.01) decreased MHPG flow; patients with psychotic features show a significantly (p < 0.05) increased MHPG excretion. The total depressive study group exhibits a homogeneous distribution where MHPG is concerned. Patients with melancholia respectively with psychotic features have shifted to the left-hand respectively right-hand tail of the Gaussian distribution.

The MHPG flow in 24 h urine is affected by the creatinine flow (p = 0.0000), the 24 h urinary output (p = 0.0003) and the age of the patient (p : 0.027). These variables should be taken into account (by means of analysis of covariance) for the interpretation of data concerning the MHPG flow.