Depression-dementia medius: between depression and the manifestation of dementia symptoms.

Depression and dementia, among the most common conditions in clinical practice, sometimes coexist, sometimes succeed each other, and often confuse clinicians. In the present paper, the clinical concept of 'depression-dementia medius' (which includes pseudodementia and depression in Alzheimer's disease as exemplars) is proposed, in reference to Janet's concept of psychological tension. Because psychosomatically complex human lives are always in a state of dynamic equilibrium, it seems sensible to propose that pseudodementia and depression in Alzheimer's disease are located within a spectrum extending from depression without dementia symptoms to dementia without depression. From the Janetian viewpoint, pseudodementia is regarded as uncovered latent dementia as a result of reduced psychological tension. Dementia is more than a fixed progressive condition under this view, and is a manifestation of dynamic mental activities. Characterizing these entities through perspectives such as psychological tension may yield deep insights in clinical practice.