A psychiatric problem is a mental disorder that affects a person's thoughts, feelings, and behavior. DEMENTIA is a common psychiatric problem that is characterized by a decline in cognitive functioning, including memory, language, problem-solving, and decision-making abilities. It is usually caused by physical changes in the brain, such as those caused by Alzheimer's disease or stroke. DEMENTIA can also be caused by other medical conditions, such as Parkinson's disease, Huntington's disease, and multiple sclerosis.