Approximately one fourth of adults in the United States have a mental illness, and nearly half will develop at least one mental illness during their lifetime (3--5). The most common mental illnesses in adults are anxiety and mood disorders (4). The effects of mental illness range from minor disruptions in daily functioning to incapacitating personal, social, and occupational impairments and premature death (6--9). In 2002 and 2003, mental illness cost the United States an estimated $300 billion annually, which included approximately $193 billion from lost earnings and wages and $24 billion in disability benefits in 2002 (10) and $100 billion in health-care expenditures in 2003 (11).

Mental illness exacerbates morbidity from the multiple chronic diseases with which it is associated, including cardiovascular disease, diabetes, obesity, asthma, epilepsy, and cancer (12--16). This increased morbidity is a result of lower use of medical care and treatment adherence for concurrent chronic diseases and higher risk for adverse health outcomes (17--20). Rates for injuries, both intentional (e.g., homicide and suicide) and unintentional (e.g., motor vehicle), are 2--6 times higher among persons with a mental illness than in the overall population (21,22). Mental illness also is associated with use of tobacco products and alcohol abuse (23).

This report summarizes data from selected CDC surveillance and information systems that measure mental illness and the associated effects in the U.S. adult population. The data presented include 1) the occurrence and associated effects of mental illness among adults in the United States as measured through selected CDC surveillance and information systems, 2) the CDC systems involved in the collection of mental illness data for adults and the associated public access databases, and 3) estimates from other studies and surveys, particularly those conducted by the Substance Abuse and Mental Health Services Administration (SAMHSA), compared with CDC system estimates.