APA Dictionary of Psychology

a heterogenous neurocognitive disorder characterized by the coexistence of two or more neuropathological processes, most commonly Alzheimer's disease (AD) pathology and vascular dementia pathology (e.g., small-vessel ischemic disease, infarcts), which leads to overlapping cognitive, behavioral, and functional symptoms. Various combinations can occur, such as AD and Lewy body disease or AD with frontotemporal lobar degeneration (less common), with symptoms depending on the underlying disease but including memory impairment (AD component), executive functioning or slowed processing speed (vascular component), or fluctuating cognitions and visual hallucinations (Lewy body component). In DSM-5 and DSM-5-TR, mixed-etiology presentations are covered by major neurocognitive disorder or mild neurocognitive disorder due to multiple etiologies.