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Bipolar disorder - Background information
What is it?

  • Bipolar disorder (also known as bipolar affective disorder or manic depressive disorder) is a serious mental illness, with a long course that is usually characterized by both episodes of depressed mood and episodes of elated mood and increased activity (hypomania or mania) [NICE, 2006; Geddes and Briess, 2008].
    • A manic episode is a distinct period during which there is abnormally and persistently elevated, expansive, or irritable mood lasting at least 1 week, accompanied by at least three additional symptoms, and which is severe enough to cause marked impairment in social or occupational functioning or necessitate hospitalization, or which includes psychotic features [DSM-IV, 1994].
    • A hypomanic episode is similar to a manic episode except that a diagnosis only requires that symptoms have lasted for 4 days, a hypomanic episode is not severe enough to cause marked impairment in social or occupational functioning or necessitate hospitalization, and there are no psychotic features [DSM-IV, 1994]. The elevation in mood may be mild [WHO, 1992].
    • A depressive episode is a period of at least 2 weeks during which there is either depressed mood or loss of interest or pleasure in nearly all activities (or irritability in children and adolescents), accompanied by at least four additional symptoms [DSM-IV, 1994]. For information on diagnosing and assessing the severity of depression, see the section on Assessment and diagnosis in the CKS topic on Depression, and the sections on Diagnosis and Assessment in the CKS topic on Depression in children.
    • A mixed episode is:
      • A mixture or rapid alternation of manic and depressive symptoms [WHO, 1992], or
      • A period of time (at least 1 week) in which the criteria are met both for a manic episode and for a depressive episode (except for duration) nearly every day, and which is sufficiently severe to cause marked impairment of occupational functioning or to require hospitalization, or there are psychotic features [DSM-IV, 1994], or
      • The presence of a mixture, or rapid alternation (usually within a few hours), of manic/hypomanic and depressive symptoms. Both sets of symptoms should be prominent for the greater part of the current episode of illness, usually for at least 2 weeks [NICE, 2006].
  • Rapid-cycling bipolar disorder is defined as the experience of at least four depressive, manic, hypomanic, or mixed episodes within a 12-month period [National Collaborating Centre for Mental Health, 2006].
  • The Diagnostic and statistical manual of mental disorders [DSM-IV, 1994] (but not the International classification of disease [ICD-10] [WHO, 1992]) makes a distinction between bipolar I disorder and bipolar II disorder:
    • Bipolar I disorder is characterized by at least one manic episode or at least two mixed episodes (with or without a history of major depressive episodes).
    • Bipolar II disorder is characterized by one or more major depressive episodes and by at least one hypomanic episode, but no evidence of mania.
  • Bipolar III disorder is recognized by some experts, and refers to hypomania or mania that develops only with antidepressant treatment [Akiskal and Pinto, 1999]. For the purposes of this summary, it is not included in the definition of bipolar disorder.

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