Distinct quality of depressed mood: an attempt to develop an objective measure

Since the time of Kraepelin, in continental Europe the sadness of depression has been considered to have a "distinct quality' basic to the diagnosis of pathological depression. This distinct quality has been interpreted by observers but patients have been noted to have difficulty verbalizing differences from normal sadness. The authors have used a discriminant analysis to study how patients define pathological sadness and as a result have developed a Pathological Sadness Index with a sensitivity of 0.94, a specificity of 0.96 and a total misclassification rate of 5% (kappa w = 0.90).