Depressive Symptoms in Clinical and Incipient Alzheimer’s Disease

The updated diagnostic criteria for Alzheimer's disease (AD) distinguish three stages: dementia, symptomatic pre-dementia [i.e. mild cognitive impairment (MCI)], and asymptomatic pre-dementia. Although AD is primarily associated with cognitive deficits, co-morbid depressive symptoms frequently occur at each stage. Depression in AD dementia is qualitatively different from depression in cognitively intact and/or younger populations, and may be less responsive to established interventions. In MCI, depressive symptoms are associated with higher rates of progression to dementia, and may identify a subset of individuals that are more responsive to acetylcholinesterase inhibitor treatment. Clinical and subsyndromal depressive symptoms in cognitively normal elderly represent a risk factor and/or prodrome for dementia due to AD, but sustained antidepressant therapy may be able to modulate this risk.