Dementia is a descriptive term for a collection of symptoms that affect the brain. As many as 6.8 million people in the United States have the condition, and at least 1.8 million of those are severely affected. People who have dementia may experience cognitive difficulties, personality changes, and behavioral problems. There is no way to reverse or stop most cases, although drugs are available to improve symptoms and slow down the disease's progression. Among the tests that a healthcare provider may use to diagnose the condition are psychiatric evaluations, cognitive and neuropsychological tests, and brain scans.