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Understanding Depression -- the Basics

What Are the Different Types of Depression? continued...

Major depression, which affects more than 16% of U.S. adults over a lifetime, often appears spontaneously and is seemingly unprovoked, or it can begin as a depressive reaction following a loss, trauma, or other significant stressful event. In people who are biologically predisposed to developing a depressive illness, the initial depressive reaction can intensify and evolve into a clinically full-blown depressive episode. The depressive episode may also disappear spontaneously, usually within six to 12 months, although medication as well as other forms of treatment are often needed to achieve full control of symptoms. Because of its disabling effects and the possibility of suicide, major depression often requires medical treatment.

  •  Dysthymia. A low-grade, long-term depression that lasts for more than one year for children and adolescents and at least two years for adults. Dysthymia is similar to depressive reaction in its symptoms and degree of suffering; however, it lasts longer and may become a chronic condition. Over the course of a lifetime, over 11% of teens (13-18) suffer from dysthymia, according to the National Institute of Mental Health.  In modern diagnostic terminology, dysthymia together with chronic major depression (that is, a major depressive episode lasting two years or longer) are both included under the category of "persistent depressive disorder."

 

What Causes Depression?

No one knows exactly what causes depression, although it appears to be an illness that may result from the interplay of many biological and environmental factors. Depressive reaction, or "normal depression," occurs as a result of a particular event. Depressed moods can also be a side effect of medication, hormonal changes (such as before menstrual periods or after childbirth), or a physical illness, such as the flu or a viral infection. Clinical depression involves a syndrome of many physical and emotional or behavioral symptoms that can occur for no apparent reason in people who are biologically vulnerable to the disorder.

Although the exact causes of major depression and dysthymia are unknown, researchers currently believe that both of these forms of depression are caused by a malfunction of brain circuits that regulate mood, thinking and behavior. Brain chemicals called neurotransmitters (such as serotonin, norepinephrine and dopamine) are important for healthy nerve cell connections; medicines that can regulate levels of these chemicals can help to fine-tune the efficiency of how these brain circuits function. 

Brain malfunctions related to depression can have a large genetic component, although genetics alone does not fully explain the risk or emergence of clinical depression. In one study, 27% of depressed children had close relatives who suffered from mood disorders.

What Are the Risk Factors for Depression?

Many factors or a combination of factors can increase the chance of depression, or make it more difficult to treat if it occurs, including:

  • Abuse. Past physical, sexual, or emotional abuse has been associated with depression later in life among people who may be biologically predisposed to depression.
  • Certain medications. For example, some drugs used to treat high blood pressure or liver disease, can increase your risk of depression.
  • Conflict. Depression may sometimes be triggered by personal conflicts or disputes with family members or friends.
  • Death or a loss. Sadness or grief from the death or loss of a loved one, though natural, can also increase the risk of depression in people who are biologically predisposed to developing it.
  • Genetics. A family history of depression may increase the risk. It's thought that depression is sometimes passed genetically from one generation to the next, similar to other complex diseases that can run in families, such as diabetes, heart disease, and cancer. The exact way this happens, though, is not known. Genetics alone, however, does not fully explain the occurrence of depression.
  • Major events. Even positive events such as starting a new job, graduating, or getting married, can lead to depression. So can moving, losing a job or income, getting divorced, or retiring.
  • Other personal problems. Problems such as social isolation due to other mental illnesses or being cast out of a family or social group can lead to depression.
  • Serious illnesses. Sometimes depression coexists with a major illness or may be triggered by a reaction to the illness.
  • Substance abuse. Nearly 30% of people with substance abuse problems also have major or clinical depression.

 

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WebMD Medical Reference

Reviewed by Joseph Goldberg, MD on April 11, 2014

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