Abuse by marriage: the exploitation of mentally ill older people.

Objectives: (i) To raise awareness about the vulnerability of mentally ill older persons to abuse by others seeking to gain by marriage; (ii) to outline key legal cases from common law countries; and (iii) to provide guidelines for health care professionals who encounter this issue in practice.

Method: We present two cases: the first case involved an 87-year-old widower who married his carer--50 years his junior--in a religious ceremony while hypomanic. The second case involved an 82-year-old widow with moderate dementia who married her boarder, the marriage subsequently being found void in the Family Court of Australia on the basis that her consent was not real because she was incapable of understanding the nature and effect of the marriage ceremony.