Mental illness contributes a substantial burden of disease worldwide. Globally, approximately 450 million persons suffer from mental disorders (1), and one fourth of the world's population will develop a mental or behavioral disorder at some point during their lives (2). Mental disorders account for approximately 25% of disability in the United States, Canada, and Western Europe and are a leading cause of premature death (1,3). In the United States, approximately 22% of the U.S. adult population has one or more diagnosable mental disorders in a given year (3). The estimated lifetime prevalences for mental disorders among the U.S. adult population are approximately 29% for anxiety disorders, 25% for impulse-control disorders, 21% for mood disorders, 15% for substance-use disorders, and 46% for any of these disorders (4). In addition, an estimated one in 10 children in the United States has a mental disorder that causes some level of impairment (5). The effects of mental illness are evident across the life span, among all ethnic, racial, and cultural groups, and among persons of every socioeconomic level (6). Moreover, mental illness costs the United States an estimated $150 billion annually, excluding the costs of research (7).

Mental health is integral to overall health and well-being and should be treated with the same urgency as physical health (3,7). Mental illness can influence the onset, progression, and outcome of other illnesses and often correlates with health risk behaviors such as substance abuse, tobacco use, and physical inactivity (8). Depression has emerged as a risk factor for such chronic illnesses as hypertension, cardiovascular disease, and diabetes and can adversely affect the course and management of these conditions (8).

Treatment for mental disorders is available and effective (3,5). However, the majority of persons with diagnosed mental disorders do not receive treatment (4). The challenges for public health are to identify risk factors, increase awareness about mental disorders and the effectiveness of treatment, remove the stigma associated with receiving treatment, eliminate health disparities, and improve access to mental health services for all persons, particularly among populations that are disproportionately affected (1,3). Public health agencies can incorporate mental health promotion into chronic disease prevention efforts, conduct surveillance and research to improve the evidence base about mental health in the United States, and collaborate with partners to develop comprehensive mental health plans to enhance coordination of care.

CDC has mobilized multiple efforts to assess and address mental health and well-being. Data on mental health, risk behaviors, and comorbidity of mental illness and chronic disease are collected through various national surveillance initiatives. CDC also collaborates with the World Federation for Mental Health to address stigma, a pervasive barrier to seeking treatment, through promotion of public awareness campaigns, such as World Mental Health Day. As the nation's premier public health agency, CDC is well-positioned to expand its role in safeguarding mental health by supporting the efforts of other health agencies, such as the Substance Abuse and Mental Health Services Administration and the National Institute of Mental Health, through continued surveillance of mental illness and risk behaviors in the U.S. population and promotion of mental health across the life span.

This issue of MMWR begins a series of occasional reports on mental health in the United States and includes a report on  attention-deficit/hyperactivity disorder in childre