Organic bases of depression in the elderly.

Early studies suggested that cerebrovascular change may be an etiological factor in the development of late-life depression. With the advent of magnetic resonance imaging (MRI), it has become possible to examine this hypothesis. MRI studies have demonstrated that patients with late-onset depression have more severe and frequent patchy lesions in the frontal deep white matter and basal ganglia than do controls or patients with early-onset depression. Patients with basal ganglia lesions, primarily caudate, are more likely to develop delirium with antidepressants and electroshock treatment (EST). The prognostic significance and the relationship of these lesions to cognitive impairment is unclear.