Depressive disorders and dementia: the clinical view.

The relationship between depression and dementia is complex. Transient emotional disturbances and long-lasting depressive disorders may occur as psychological reactions to the loss of mental abilities or as behavioural manifestations of brain injury. On the other hand, major depressive disorder of late onset or of a recurrent type may be superimposed on dementing illness. Depression, particularly in elderly individuals, can manifest itself as a reversible syndrome of dementia that responds favourably to antidepressant treatment. It is not known whether the dementia syndrome of depression represents a quantitative intensification of minor cognitive impairments that can be observed in a large proportion of depressed patients. It also remains doubtful whether dementia in depressed patients has to be considered as an epiphenomenon of pervasive melancholic illness. An alternative explanation would look at such conditions as manifestations of a specific brain dysfunction. Major depression associated with cognitive impairment in stroke patients might be regarded as an example of a reversible dementia dysfunction.