Dementia occurs as a set of related symptoms when the brain is damaged by injury or disease. The symptoms involve progressive impairments to memory, thinking, and behavior, that affect the ability to look after oneself as a measure of carrying out everyday activities. Other common symptoms include emotional problems, difficulties with language, and decreased motivation. The symptoms may be described as occurring in a continuum over several stages. Dementia is not a disorder of consciousness, and consciousness is not usually affected. A diagnosis of dementia requires a change from a person's usual mental functioning, and a greater cognitive decline than that due to normal aging. Several diseases, and injuries to the brain such as a stroke, can give rise to dementia. However, the most common cause is Alzheimer's disease a neurodegenerative disorder. Dementia has a significant effect on the individual, relationships and caregivers. In DSM-5, dementia has been reclassified as a major neurocognitive disorder, with varying degrees of severity, and many causative subtypes.