Old age depression is often difficult to discriminate from dementia (particularly of Alzheimer type) – particularly cross-sectionally. Incident dementia is frequently associated with depressed mood and agitation; depression in the elderly goes together with executive and memory dysfunctions; associated psychotic symptoms and activity-of-daily-life dysfunctions are shared by both conditions as well as major risk factors as vascular and metabolic factors. Frequently both syndromes are “masking” each other; depression may furthermore present as the first clinical sign of Alzheimers disease.

Yet, both clinical syndromes/disorders emerging from quite different are pathogenic neurobiological mechanisms with differentiating neuropsychological, – imaging and – chemical features. Clinical tools can be derived and enable accurate differential diagnosis. Thus, the distinction between both syndromes is a first instance for biomarker supported differential diagnoses in psychiatry.