The fact that there is a need for assessing depression, whether as an affect, a symptom, or a disorder is obvious by the numerous scales and inventories available and in use today.
The need to assess depression simply and specifically as a psychiatric disorder has not been met by most scales available today. We became acutely aware of this situation in a research project where we needed to correlate both the presence and severity of a depressive disorder in patients with other parameters such as arousal response during sleep and changes with treatment of the depressive disorder. It was felt that the general depression scales used were insufficient for our purpose and that the more specific scales were also inadequate. These inadequacies related to factors such as the length of a scale or inventory being too long and too time consuming, especially for a patient
ZUNG WWK. A Self-Rating Depression Scale. Arch Gen Psychiatry. 1965;12(1):63–70. doi:10.1001/archpsyc.1965.01720310065008