Mental deterioration is a term used to describe the decline of cognitive abilities, such as memory, language, and problem-solving. DEMENTIA is a common form of mental deterioration, which is characterized by a progressive decline in cognitive functioning. It is often caused by diseases such as Alzheimer's or Parkinson's, but can also be caused by other conditions such as stroke, head trauma, or drug abuse. DEMENTIA can lead to significant changes in behavior, personality, and social functioning, and can have a major impact on the quality of life of those affected.