This entry covers the psycholegal concept of capacity in adulthood and describes legal guardianship of adults. The capacity to manage oneself and one’s affairs depends on a variety of factors, including health, functional abilities, and mental status. Prior to age 18, individuals in most jurisdictions in the United States are presumed to lack capacity over themselves and their financial affairs and have a parent or guardian who makes such decisions. Adults are generally presumed to have capacity unless determined otherwise in a medical or legal context.

Medical and mental illnesses, including developmental delays, brain trauma, severe illness, or dementia, may interfere with capacity on a temporary or permanent basis throughout adulthood. Older adults can be particularly vulnerable to incapacity; medical and mental health issues common to ...