Diurnal variation: reliability of measurement and relationship to typical and atypical symptoms of depression.

We used three rating scales to study diurnal variation of mood in 37 patients with major depressive disorder (17 drug-free patients and 20 treatment refractory patients on stable regimens of antidepressant medication). The three rating scales included global self-ratings administered twice a day; an itemized, prospective, observer-rated scale administered twice a day; and the retrospective item on the Hamilton Depression Rating Scale. Z scores and Intraclass Correlation Coefficients demonstrated a poor level of agreement between the itemized, prospective scale and the self-ratings. In addition, stepwise multiple regression analysis and point bi-serial correlation showed no systematic relationship between atypical diurnal variation (i.e., mood worsening in the evening) and atypical depressive symptoms (weight gain, hypersomnia, etc.), or between typical diurnal variation (i.e., mood worsening in the morning) and typical depressive symptoms (weight loss, insomnia, etc.). This lack of relationship was observed in both drug-free and medicated patients using each of the three rating scales. We discuss possible explanations for these negative findings.