Dementia comprises multiple cognitive (thinking) deficits including the inability to retain new information and recall previously learned information. It arises not only in Alzheimer's Disease, but in Vascular Dementia where the blood supply to the brain in interrupted or blocked. Dementia can result from the intake (intentionally or accidentally) of substances and can also be due to a variety of medical conditions that effect the central nervous system. There can be mood changes, behavioral disturbances, delusions and delirium (reduced clarity of awareness of the environment).

Dementia presented as memory impairment (both inability to learn new material and to recall old material), along with cognitive problems such as language disturbance (aphasia), inability to carry out motor activities (apraxia) or inability to recognize objects (agnosia) can arise from HIV Disease, Head Trauma, Parkinson's Disease, Huntington's Disease, Pick's Disease, Creutzfeldt-Jakob Disease and others. Dementia can also be the longstanding and perhaps permanent impact of substances ingested. Obviously, dementia can, for some individuals, be the combined result of multiple factors.

Amnestic Disorder, the impairment in the ability to learn new information or recall previously learned material, can be transient or chronic. It can be substance induced or can be the result of a disease process. It is only one component of the dementia seen in Alzheimer's Disorder (in which there may be language disturbance, inability to carry out motor activities (apraxia), failure to recognize familiar objects (agnosia) and/or inability to organize, plan, etc (executive functioning). Amnestic Disorder is confined to memory difficulty and is not associated with the mood, delusional and behavioral complications of Alzheimer's Disorder.