Geriatric depression: age of onset and dementia.

Age of depression onset was studied in 183 consecutively hospitalized elderly patients with major depression. Patients with both depression and dementia had onset of depression at a significantly later age than patients with depression alone. Depressives with reversible dementia had age of onset comparable to that of depressives with irreversible dementia. These findings suggest that late-onset depression is a heterogeneous syndrome and includes a considerable number of patients who develop depression as part of a dementing illness.