A diagnosis of “major neurocognitive disorder”, also known as dementia, is given when there is evidence of significant cognitive decline from a previous level of performance in one or more cognitive domains: complex attention, executive function, learning, and memory, language, perceptual-motor, or social cognition. The diagnosis is based on:

• Concern of the individual, a knowledgeable informant, or the clinician that there has been a significant decline in cognitive function; and
• A substantial impairment in cognitive performance, preferably documented by standardized neuropsychological testing, or in its absence, another quantified clinical assessment.

The cognitive deficits interfere with the individual’s independence in everyday activities, at a minimum, requiring assistance with activities of daily living such as paying bills or managing medications. The cognitive impairment does not occur exclusively in the context of delirium and is not better explained by another mental disorder (e.g., major depressive disorder, schizophrenia).

The major neurocognitive disorder may be due to:

• Alzheimer’s disease
• Frontotemporal lobar degeneration
• Lewy body disease
• Vascular disease
• Traumatic brain injury
• Substance/medication use
• HIV infection
• Prion Disease
• Parkinson’s disease
• Huntington’s disease
• Another medical condition
• Multiple medical conditions
• An unspecified cause