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The Invisible Disease: Depression

Depression is a serious medical condition. In contrast to the normal emotional experiences of sadness, loss, or passing mood states, clinical depression is persistent and can interfere significantly with an individual's ability to function. There are three main types of depressive disorders: major depressive disorder, dysthymic disorder, and bipolar disorder (manic-depressive illness).

Symptoms and Types of Depression

Symptoms of depression include sad mood, loss of interest or pleasure in activities that were once enjoyed, change in appetite or weight, difficulty sleeping or oversleeping, physical slowing or agitation, energy loss, feelings of worthlessness or inappropriate guilt, difficulty thinking or concentrating, and recurrent thoughts of death or suicide. A diagnosis of major depressive disorder is made if a person has 5 or more of these symptoms and impairment in usual functioning nearly every day during the same two-week period. Major depression often begins between ages 15 to 30 but also can appear in children. 1 Episodes typically recur.

Some people have a chronic but less severe form of depression, called dysthymic disorder, which is diagnosed when depressed mood persists for at least 2 years (1 year in children) and is accompanied by at least 2 other symptoms of depression. Many people with dysthymia develop major depressive episodes.

Episodes of depression also occur in people with bipolar disorder. In this disorder, depression alternates with mania, which is characterized by abnormally and persistently elevated mood or irritability and symptoms including overly-inflated self-esteem, decreased need for sleep, increased talkativeness, racing thoughts, distractibility, physical agitation, and excessive risk taking. Because bipolar disorder requires different treatment than major depressive disorder or dysthymia, obtaining an accurate diagnosis is extremely important.

Facts About Depression

  • Major depression is the leading cause of disability in the U.S. and worldwide. 2
  • Depressive disorders affect an estimated 9.5 percent of adult Americans ages 18 and over in a given year, 3 or about 18.8 million people in 1998. 4
  • Nearly twice as many women (12 percent) as men (7 percent) are affected by a depressive disorder each year. 3

Depression can be devastating to family relationships, friendships, and the ability to work or go to school. Many people still believe that the emotional symptoms caused by depression are "not real," and that a person should be able to shake off the symptoms. Because of these inaccurate beliefs, people with depression either may not recognize that they have a treatable disorder or may be discouraged from seeking or staying on treatment due to feelings of shame and stigma. Too often, untreated or inadequately treated depression is associated with suicide. 5


Antidepressant medications are widely used, effective treatments for depression. 6 Existing antidepressants influence the functioning of certain chemicals in the brain called neurotransmitters. The newer medications, such as the selective serotonin reuptake inhibitors (SSRIs), tend to have fewer side effects than the older drugs, which include tricyclic antidepressants (TCAs) and monoamine oxidase inhibitors (MAOIs). Although both generations of medications are effective in relieving depression, some people will respond to one type of drug, but not another. Other types of antidepressants are now in development.

Certain types of psychotherapy, specifically cognitive-behavioral therapy (CBT) and interpersonal therapy (IPT), have been found helpful for depression. Research indicates that mild to moderate depression often can be treated successfully with either therapy alone; however, severe depression appears more likely to respond to a combination of psychotherapy and medication. 7 More than 80 percent of people with depressive disorders improve when they receive appropriate treatment. 8

In situations where medication, psychotherapy, and the combination of these interventions prove ineffective, or work too slowly to relieve severe symptoms such as psychosis (e.g., hallucinations, delusional thinking) or suicidality, electroconvulsive therapy (ECT) may be considered. ECT is a highly effective treatment for severe depressive episodes. The possibility of long-lasting memory problems, although a concern in the past, has been significantly reduced with modern ECT techniques. However, the potential benefits and risks of ECT, and of available alternative interventions, should be carefully reviewed and discussed with individuals considering this treatment and, where appropriate, with family or friends. 9

One herbal supplement, hypericum or St. John's wort, has been promoted as having antidepressant properties. Results from the first large-scale, controlled study of St. John's wort for major depression, which was funded in part by NIMH, are expected in 2001. Note: There is evidence that St. John's wort can reduce the effectiveness of certain medications. Use of any herbal or natural supplements should always be discussed with your doctor before they are tried.

Research Findings

  • Brain imaging research is revealing that in depression, neural circuits responsible for moods, thinking, sleep, appetite, and behavior fail to function properly, and that the regulation of critical neurotransmitters is impaired. 10
  • Genetics research, including studies of twins, indicates that genes play a role in depression. Vulnerability to depression appears to result from the influence of multiple genes acting together with environmental factors. 11
  • Other research has shown that stressful life events, particularly in the form of loss such as the death of a close family member, may trigger major depression in susceptible individuals. 12
  • The hypothalamic-pituitary-adrenal (HPA) axis, the hormonal system that regulates the body's response to stress, is overactive in many people with depression. Research findings suggest that persistent overactivation of this system may lay the groundwork for depression. 13
  • Studies of brain chemistry, mechanisms of action of antidepressant medications, and the cognitive distortions and disturbed interpersonal relationships commonly associated with depression, continue to inform the development of new and better treatments.


1 Birmaher B, Ryan ND, Williamson DE, et al. Childhood and adolescent depression: a review of the past 10 years. Part I. Journal of the American Academy of Child and Adolescent Psychiatry, 1996; 35(11): 1427-39.

2 Murray CJL, Lopez AD, eds. Summary: The global burden of disease: a comprehensive assessment of mortality and disability from diseases, injuries, and risk factors in 1990 and projected to 2020. Cambridge, MA: Published by the Harvard School of Public Health on behalf of the World Health Organization and the World Bank, Harvard University Press, 1996.

3 Regier DA, Narrow WE, Rae DS, et al. The de facto mental and addictive disorders service system. Epidemiologic Catchment Area prospective 1-year prevalence rates of disorders and services. Archives of General Psychiatry, 1993; 50(2): 85-94.

4 Narrow WE. One-year prevalence of depressive disorders among adults 18 and over in the U.S.: NIMH ECA prospective data. Population estimates based on U.S. Census estimated residential population age 18 and over on July 1, 1998. Unpublished.

5 Conwell Y, Brent D. Suicide and aging I: patterns of psychiatric diagnosis. International Psychogeriatrics, 1995; 7(2): 149-64.

6 Mulrow CD, Williams JW Jr., Trivedi M, et al. Evidence report on treatment of depression-newer pharmacotherapies. Psychopharmacology Bulletin, 1998; 34(4): 409-795.

7 Hyman SE, Rudorfer MV. Depressive and bipolar mood disorders. In: Dale DC, Federman DD, eds. Scientific American¨ Medicine. Volume 3. New York: Healtheon/WebMD Corp., 2000, Sect. 13, Subsect. II, p. 1.

8 National Advisory Mental Health Council. Health care reform for Americans with severe mental illnesses. American Journal of Psychiatry, 1993; 150(10): 1447-65.

9 U.S. Department of Health and Human Services. Mental health: a report of the Surgeon General. Rockville, MD: U.S. Department of Health and Human Services, Substance Abuse and Mental Health Services Administration, Center for Mental Health Services, National Institutes of Health, National Institute of Mental Health, 1999.

10 Soares JC, Mann JJ. The functional neuroanatomy of mood disorders. Journal of Psychiatric Research, 1997; 31(4): 393-432.

11 NIMH Genetics Workgroup. Genetics and mental disorders. NIH Publication No. 98-4268. Rockville, MD: National Institute of Mental Health, 1998.

12 Mazure CM, Bruce ML, Maciejewski PW, et al. Adverse life events and cognitive-personality characteristics in the prediction of major depression and antidepressant response. American Journal of Psychiatry, 2000; 157(6): 896-903.

13 Arborelius L, Owens MJ, Plotsky PM, et al. The role of corticotropin-releasing factor in depression and anxiety disorders. Journal of Endocrinology, 1999; 160(1): 1-12.

Source: The National Institute of Mental Health, NIH Publication No. 01-4591, January 01, 2001



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