Affective illness, dementia, and pseudodementia.

The differential diagnosis and treatment of pseudodementia, dementia, and depressive illness are receiving increased attention. The literature on this subject is reviewed, and four "ideal types" of patients spanning the spectrum of these illnesses are proposed for use when their distinction or association is at issue. Attempts by investigators to distinguish those groups are summarized, ad the importance of diagnostic clarity and patient selection for future research is emphasized.