Treatment-resistant depression in the elderly.

Apparent treatment-resistant depression (TRD) is frequently encountered by and poses particular challenges for the old-age psychiatrist. The prevalence of true nonresponse to treatment is not known with accuracy but reports put it at 18% to 40% for the elderly. This article reviews the concept of TRD in the elderly, discussing the factors involved in apparent resistance and the treatment of this group. We suggest that absolute TRD may be a rarer entity than the estimated 18% to 40% if depressed patients are treated carefully and vigorously.