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Depression Health Center

Understanding Depression -- the Basics

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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. 

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