Typus melancholicus has been considered to be a distinguishing premorbid personality trait of unipolar depressive patients in Japan and Germany where premorbid personality has been studied chiefly by categorical approach. However, from psychometric point of view the available evidence is inconclusive as to typus melancholicus as the specific premorbid personality of unipolar depression. Further studies are needed to confirm the association between typus melancholicus and unipolar course or between typus manicus and bipolar course that has been suggested by von Zerssen. As to categorical approach, prospective study is needed in consideration of the importance of representative sampling and the validity of assessment of typus melancholicus. Dimensional approach has not found any premorbid personality trait specific to unipolar depression, which would not contribute to everyday practice. Nevertheless, dimensional approach contributes to the development of researches in pursuit of genetic factors in personality trait. Differences in premorbid personality trait between unipolar and bipolar patients suggest that genetic factors of mood disorder could also contribute to the formation of premorbid personality.