Depression is a term used in several ways to mean different things. It is used in casual conversation to describe being sad, discouraged, or frustrated. It is a symptom, which often accompanies a variety of medical diagnoses relating to chronic pain, traumatic brain injury, hypothyroidism, chronic illnesses, and other medical conditions. It is also a feature of many mental disorders and represents one of the most common mental health diagnoses (major depressive disorder).

Depression is characterized by the presence of a sad, low or irritable mood that affects an individual’s capacity to function[1]. Depressive disorders are common, yet under diagnosed and undertreated mental health conditions that are a foremost cause of impaired quality of life, reduced productivity, and increased mortality in the United States[2]. According to the Centers for Disease Control, the prevalence of individuals with depression in the United States is approximately 8 percent during any two-week period[3]. Current prevalence rates likely underestimate the true occurrence of depressive disorders because many individuals with depression never seek treatment[4]. The annual economic burden of depression in the United States was estimated to be almost $210 billion in the year 2010, with 45-47 percent attributed to direct costs, 5 percent to suicide-related costs, and 48-50 percent to workplace costs[5].

Depression is caused by a combination of genetic, biological, environmental, and psychological factors[6]. Individuals with depression frequently report somatic complaints, such as fatigue, loss of energy, and difficulty sleeping, among other symptoms, rather than specific complaints of depressed mood. Depressive disorders are diagnosed when a persistent low mood and an absence of positive affect are accompanied by a range of symptoms, which may include loss of interest in most activities (anhedonia), significant change in weight or appetite, insomnia or hypersomnia, decreased concentration, inappropriate guilt or feelings of worthlessness, psychomotor agitation or retardation, and/or suicidal ideation[7]. There are several, depressive disorders, including major depressive disorder, persistent depressive disorder (dysthymia), premenstrual dysphoric disorder, substance/medication-induced depressive disorder, and other less common depressive disorders[8]. Depression is frequently recurrent and can be a chronic condition. Individuals with depression are at increased risk of suicide and depression is a significant independent risk factor for a number of medical conditions including first myocardial infarction and cardiovascular mortality[9].

Service members returning from combat deployments are at increased risk for development of depression[10]. For instance, research studies found that 7-14 percent of service members returning from Operation Enduring Freedom (OEF) and 8-15 percent of service members returning from Operation Iraqi Freedom (OIF) met the screening criteria for major depressive disorder[11].

Annual screening for depression in the primary care setting is recommended using a standardized assessment tool. Mild forms of depression can be effectively treated with either medication or psychotherapy, while more moderate to severe forms may require an approach that combines psychotherapy and medication for effective treatment. Education and support are essential factors for both mild and severe forms of depression. The Department of Veterans Affairs (VA) and the Department of Defense (DoD) developed the VA/DoD Clinical Practice Guideline for Management of Major Depressive Disorder (MDD) to assist providers through provision of clear and comprehensive evidence-based recommendations in the management of MDD to “improve patient outcomes and local management of patients with MDD.” For further information about this clinical practice guideline and the related clinical support tools, please visit the Treatment Guidance section.


  1. American Psychiatric  Association. (2013). Diagnostic and  statistical manual of mental disorders (5th ed.) Arlington, VA: American  Psychiatric Publishing.
  2.  National Institute of  Mental Health (NIMH). (n.d.). NIMH causes  of depression. Retrieved from

  3. Centers for Disease  Control. (2015). Depression. Retrieved  from

  4.  National Quality  Management Program - Lockheed Martin Federal Healthcare. (2004). Depression: Detection, management, and  comorbidity in the Military Health System. Alexandria, VA: Birch & Davis.

  5.  Greenberg, P.E.,  Fournier, A., Sisitsky, T., Pike, C.T., & Kessler, R.C. (2015). The  economic burden of adults with major depressive disorder in the United States  (2005 and 2010). Journal of Clinical  Psychiatry, 76 (2), 155-162.

  6. National Institute of  Mental Health (NIMH). (n.d.). NIMH causes  of depression. Retrieved from

  7.  National  Collaborating Centre for Mental Health (UK). (2010). Depression: The treatment and management of depression in adults  (Updated Edition). Leicester (UK): British Psychological Society. Retrieved  from

  8. American Psychiatric  Association. (2013). Diagnostic and  statistical manual of mental disorders (5th ed.). Arlington, VA: American  Psychiatric Publishing.

  9. Management of Major  Depressive Disorder Working Group (2009). VA/DoD  clinical practice guideline for management of major depressive disorder.  Retrieved from

  10. Gadermann, A.M.,  Engel, C.C., Naief, J.A., Nock, M.K., Petukhova, M., Santiago, P.N., Benjamin,  W., Zaslavasky, A.M., & Kessler, R. (2012). Prevalence of DSM-IV major  depression among U.S. military personnel: Meta-analysis and simulation. Military Medicine, 177(8), 47-59. 

    Kessler,  R.C., Heeringa, S.G., Stein, M.B., Colpe, L.J., Fullerton, C.S., Hwang, I.,  Naifeh, J.A., Nock, M.K., Petukhova, M., Sampson, N.A., Schoenbaum, M.,  Zaslavsky, A.M., & Ursano, R. Thirty-day prevalence of DSM-IV mental  disorders among nondeployed soldiers in the US Army: Results from the army  study to assess risk and resilience in servicemembers (Army STARRS). Journal of the American Medical Association  Psychiatry, 71 (5), 504-513.

  11. Hoge, C.W.,  Auchterlonie, J.L., & Milliken C.S. (2006). Mental health problems, use of  mental health services, and attrition from military service after returning  from deployment to Iraq or Afghanistan. Journal  of the American Medical Association, 295(9), 1023-32.

    Hoge,  C.W., Castro, C.A., Messer, S.C., McGurk, D., Cotting, D.I., Koffman, R.L.  (2004). Combat duty in Iraq and Afghanistan, mental health problems, and  barriers to care. New England Journal of  Medicine, 351(1), 13-22.