About Mental Health

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What is mental health?

Mental health includes our emotional, psychological, and social well-being. It affects how we think, feel, and act. It also helps determine how we handle stress, relate to others, and make healthy choices.1 Mental health is important at every stage of life, from childhood and adolescence through adulthood.

Although the terms are often used interchangeably, poor mental health and mental illness are not the same. A person can experience poor mental health and not be diagnosed with a mental illness. Likewise, a person diagnosed with a mental illness can experience periods of physical, mental, and social well-being.


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Why is mental health important for overall health?

Mental and physical health are equally important components of overall health.  For example, depression increases the risk for many types of physical health problems, particularly long-lasting conditions like diabetes, heart disease, and stroke. Similarly, the presence of chronic conditions can increase the risk for mental illness.2


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Can your mental health change over time?

Yes, it’s important to remember that a person’s mental health can change over time, depending on many factors.  When the demands placed on a person exceed their resources and coping abilities, their mental health could be impacted. For example, if someone is working long hours, caring for a relative, or experiencing economic hardship, they may experience poor mental health.


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How common are mental illnesses?

Mental illnesses are among the most common health conditions in the United States.

  • More than 50% will be diagnosed with a mental illness or disorder at some point in their lifetime.3
  • 1 in 5 Americans will experience a mental illness in a given year.4
  • 1 in 5 children, either currently or at some point during their life, have had a seriously debilitating mental illness.5
  • 1 in 25 Americans lives with a serious mental illness, such as schizophrenia, bipolar disorder, or major depression.6

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What causes mental illness?

There is no single cause for mental illness. A number of factors can contribute to risk for mental illness, such as

  • Early adverse life experiences, such as trauma or a history of abuse (for example, child abuse, sexual assault, witnessing violence, etc.)
  • Experiences related to other ongoing (chronic) medical conditions, such as cancer or diabetes
  • Biological factors or chemical imbalances in the brain
  • Use of alcohol or drugs
  • Having feelings of loneliness or isolation

People can experience different types of mental illnesses or disorders, and they can often occur at the same time. Mental illnesses can occur over a short period of time or be episodic. This means that the mental illness comes and goes with discrete beginnings and ends. Mental illness can also be ongoing or long-lasting.

There are more than 200 types of mental illness. Some of the main types of mental illness and disorders are listed hereexternal icon.

  1. Strengthening Mental Health Promotionexternal icon. Fact sheet no. 220. Geneva, Switzerland: World Health Organization.
  2. Chronic Illness & Mental Healthexternal icon. Bethesda, MD: National Institutes of Health, National Institute of Mental Health. 2015.
  3. Kessler RC, Angermeyer M, Anthony JC, et al. Lifetime prevalence and age-of-onset distributions of mental disorders in the World Health Organization’s World Mental Health Survey Initiative. World Psychiatry. 2007;6(3):168-176.
  4. Key substance use and mental health indicators in the United States: Results from the 2015 National Survey on Drug Use and Health. Rockville, MD: Center for Behavioral Health Statistics and Quality. Substance Abuse and Mental Health Services Administration. 2016.
  5. Merikangas KR, He J, Burstein M, et al. Lifetime Prevalence of Mental Disorders in US Adolescents: Results from the National Comorbidity Study-Adolescent Supplement (NCS-A). Journal of the American Academy of Child and Adolescent Psychiatry. 2010;49(10):980-989. doi:10.1016/j.jaac.2010.05.017.
  6. Key substance use and mental health indicators in the United States: Results from the 2015 National Survey on Drug Use and Health. Rockville, MD: Center for Behavioral Health Statistics and Quality. Substance Abuse and Mental Health Services Administration. 2016.
  7. Health & Education Statisticsexternal icon. Bethesda, MD: National Institute of Mental Health. National Institutes of Health. 2016.
  8. Kessler RC, Chiu WT, Demler O, Walters EE. Prevalence, Severity, and Comorbidity of Twelve-month DSM-IV Disorders in the National Comorbidity Survey Replication (NCS-R). Archives of general psychiatry. 2005;62(6):617-627. doi:10.1001/archpsyc.62.6.617.Substance Abuse and Mental Health Services Administration, Center for Behavioral Health Statistics and Quality. (2016). Key substance use and mental health indicators in the United States: Results from the 2015 National Survey on Drug Use and Health. Rockville, MD.
  9. Rui P, Hing E, Okeyode T. National Ambulatory Medical Care Survey: 2014 State and National Summary Tables.pdf icon Atlanta, GA: National Center for Health Statistics. Centers for Disease Control and Prevention. 2014.
  10. Web-based Injury Statistics Query and Reporting System (WISQARS). Atlanta, GA: National Center for Injury Prevention and Control. Centers for Disease Control and Prevention. 2015.
  11. Insel, T.R. Assessing the Economic Costs of Serious Mental Illness. Am J Psychiatry. 2008 Jun;165(6):663-5. doi: 10.1176/appi.ajp.2008.08030366.
  12. HCUP Facts and Figures: Statistics on Hospital-based Care in the United States, 2009. Rockville, MD: Agency for Healthcare Research and Quality. 2009.
  13. Reeves, WC et al. CDC Report: Mental Illness Surveillance Among Adults in the United States. MMWR Morb Mortal Wkly Rep 2011;60(03);1-32.
  14. Parks, J., et al. Morbidity and Mortality in People with Serious Mental Illness. Alexandria, VA: National Association of State Mental Health Program Directors Council. 2006.
  15. Strengthening Mental Health Promotionexternal icon. Fact sheet no. 220. Geneva, Switzerland: World Health Organization.