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Mental Health Disorders

Medically reviewed by L. Anderson, PharmD Last updated on Sep 11, 2017.

Mental health disorders are common affecting tens of millions of people each year in the United States. However, overall, only about half of those affected receive treatment. The National Survey on Drug Use and Health (NSDUH) defines a mental illness (AMI) as:

  • A mental, behavioral, or emotional disorder (excluding developmental and substance use disorders)
  • Diagnosable currently or within the past year
  • Meets diagnostic criteria specified within the Diagnostic and Statistical Manual of Mental Disorders.

A mental illness does not mean one cannot function and live a productive life; treatments can have a profound effect. AMI can range in impact from limited impairment to significantly disabling impairment, such as in individuals with serious mental illness (SMI). A serious mental illness is defined as individuals with a mental disorder with serious functional impairment which substantially interferes with or limits one or more major life activities.

Common mental health disorders include:

In 2015, there were roughly 43 million U.S. adults aged 18 or older with any mental illness, equal to about 18% of all U.S. adults. The prevalence of any mental illness was higher among women than men (21% vs. 14%) and higher among whites (19%) than in Hispanics (14%), Blacks (15%), or Asians (12%). The age groups 18 to 49 years have an increased prevalence for mental health disorders (roughly 21%) than older adults over 50 years of age (14%).

Even though mental disorders are widespread, the main burden of illness lies in serious mental health disorders. As reported in 2015 in the previous year, serious mental disorders are concentrated in about 9.8 million adults, or about 4% of the U.S. adult population. These result in serious functional impairment, which substantially interferes with or limits one or more major life activities. These estimates of any mental illness do not include substance use disorders, such as drug- or alcohol-related disorders.

Mental illnesses can take a financial toll on the nation as well as the individual. Major depressive disorder is the leading cause of disability in the U.S. for individuals aged 15 to 44 years. Mental health disorders are also high among the homeless and inmates. Add to that, cuts in government-funded mental health services and psychiatric hospital beds, and the cost of not caring for these patients can be multiplied.


See Also


  • National Institute of Mental Health. Any Mental Illness (AMI) Among U.S. Adults. Accessed September 11, 2017 at

Further information

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