Is diurnal variation a meaningful symptom in unipolar depression?

The present study found that defining groups of patients based on the presence or absence of diurnal variation highlighted several important differences between the two groups. Diurnal patients had longer episodes, better response to treatment, and were less frequently classified as RDC agitated. Within this diurnal population, evening sufferers had more decrease in appetite than morning sufferers. Equivalent percentages of diurnal-a.m. and diurnal-p.m. received RDC endogenous diagnoses, but more diurnal-a.m. patients were found in the DSM-III melancholia category. While this study found some evidence inconsistent with the generally accepted notion regarding the constellation of symptoms associated with endogenous and non-endogenous depressions, the authors suggest that diurnal variation may represent a predictor of unipolar depression which is biologically based.