Treatment-resistant depression in late life.

Depression is the most prevalent functional psychiatric disorder in late life. It is associated with a high risk of mortality from comorbid medical illness and from suicide. Successful antidepressant treatment is one of the most effective ways to reduce disability, prevent morbidity, and improve quality of life in an older depressed patient. Treatment-resistant depression is a common clinical problem, reported to affect up to one-third of older depressed patients. However, published data on this clinically important topic are sparse. Available data and clinical experience indicate that many depressed patients labeled as "treatment resistant" or even "treatment refractory" are so labeled because of variables involving the diagnostic or treatment process, rather than because they suffer from a depression that is truly unresponsive to treatment. Unidentified comorbid medical or psychiatric conditions and misdiagnosis often contribute to treatment resistance. Atypical depressive symptoms, such as somatic and cognitive symptoms, and comorbid medical conditions that can themselves produce depressive symptoms often make it difficult to accurately assess antidepressant response in this age group. This often leads to inadequate pharmacotherapy, another major factor contributing to apparent treatment resistance. In older patients, as in younger patients, the selection of the right antidepressant, the right dose, and the right treatment duration constitute the treatment variables essential in ensuring optimal therapeutic response. Approach to treatment-resistant depression in the elderly involves reconsideration of the diagnosis and use of alternate therapeutic measures in a systematic way, including switching to another agent, combination therapy, and electroconvulsive therapy.