Depressive dementia: a "transitional dementia"?

This review comprises a historical, clinical, and empirical examination of the dementia spectrum of depression. The primary focus of the article is to evaluate the usual dichotomy between depressive dementia as functional-reversible and degenerative dementia as organic-irreversible. It is proposed that depression, cognitive impairment, and degenerative dementia be viewed as intersecting continua. Five prototypical groups are defined along these continua: (1) major depression without depressive dementia, (2) depressive dementia, (3) degenerative dementia without depression, (4) depression of degenerative dementia, and (5) random co-occurrence of depression and degenerative dementia. The data suggest that a subset of cases of major depression without dementia appear to evolve into depressive dementia, and in turn, depressive dementia may constitute a risk factor for degenerative dementia. Depressive dementia and degenerative dementia can sometimes represent two different points of organic deterioration and severity in a long-term, multiphasic disease course; depressive dementia sometimes appears to be a transitional stage or phase in a disease progression from depression without dementia to a degenerative dementia. The concept of "transitional dementia" is introduced in a heuristic and preliminary attempt to accommodate the nosologic entity of depressive dementia.