Frequent users of emergency departments: the myths, the data, and the policy implications.

Frequent emergency department (ED) users have been the targets of health care reform proposals and hospital crowding interventions, but it is not clear that common assumptions about this group are supported by data. We review the literature pertaining to frequent ED users, their demographics, acuity of illness, and patterns of health care utilization. We seek to inform development of policies directed at frequent ED use and to highlight potential related challenges.