Dementia is a condition of mental decline that usually comes on slowly over several months. It involves memory, problem-solving and learning abilities, and other mental functions. Little change is noticed day to day, although many people with dementia seem better or worse at different times of the day.

Many health conditions can cause dementia or symptoms similar to dementia. In some cases dementia may be reversible. Alzheimer's disease is the most common cause of dementia in people over age 65.

Early signs of dementia include the following.

• Behavior changes, such as:
  • A normally tidy person becomes messy
  • A change in previous routines for no obvious reason
  • A decline in language and communication skills
  • Paranoia and suspicions of others
• Personality changes, such as:
  • Agitation
  • Depression
  • Social withdrawal
  • Unusual behavior
  • Wide mood swings
• Skill changes, such as an inability to:
  • Balance a checkbook
  • Perform self-care acitivities, such as shaving or putting on makeup
  • Cook a favorite recipe
  • Find previously familiar places
  • Remember times and dates
  • Remember where familiar items are kept

A young person who has symptoms of dementia is more likely to have a psychiatric condition or a substance abuse problem than early dementia.

Over time, mental impairment from dementia will become severe enough to interfere with daily living activities.