The diagnostic criteria for major depression in the Diagnostic and Statistical Manual of Mental Disorders, fifth edition (DSM-5), require the presence of either sadness or anhedonia with a total of five or more symptoms over a 2-week period (Table 1TABLE 1
DSM-5 Diagnostic Criteria for Major Depressive Disorder.
). Low mood may be less common in older adults with depression than in younger adults with the disorder, whereas irritability, anxiety, and somatic symptoms may be more common. Psychosocial stressors such as the death of a loved one may trigger a depressive episode, although transient reactions to major losses can resemble depression. In DSM-5, unlike previous editions, grief after the death of a loved one is not considered to be exclusionary.
Coexisting medical illness complicates the management of depression. Persons with late-life depression have higher rates of coexisting conditions and concomitant medication use than their nondepressed counterparts. The relationship between depression and a coexisting medical illness may be bidirectional: medical problems such as chronic pain may confer a predisposition to depression, and depression is associated with worse outcomes for conditions such as cardiac disease. 7 Coexisting illness raises concerns about polypharmacy, including the effects of psychotropic drugs on medical conditions and the metabolism of other medications. Age-related declines in drug metabolism may also contribute to increased rates of medication side effects.
Coexisting cognitive impairment is common in persons with late-life depression and can involve multiple cognitive domains, including executive function, attention, and memory. Depression may be both a risk factor for and a manifestation of cognitive decline: depression is associated with an increased long-term risk of dementia.8 Cognitive deficits may thus be signs of accelerated brain aging that confers a predisposition to and perpetuates depression.6