Family, twin, and adoption studies of bipolar disorder


  • Jordan W. Smoller,

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    • Jordan W. Smoller is Assistant Professor of Psychiatry at Harvard Medical School and Director of the Psychiatric Genetics Program in Mood and Anxiety Disorders in the Outpatient Division of the Massachusetts General Hospital Department of Psychiatry.

  • Christine T. Finn

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    • Christine T. Finn is a psychiatrist at Massachusetts General Hospital and a clinical fellow in genetics in the Harvard Medical School genetics training program.


Family, twin, and adoption studies have been essential in defining the genetic epidemiology of bipolar disorder over the past several decades. Family studies have documented that first-degree relatives of affected individuals have an excess risk of the disorder, while twin studies (and to a lesser extent, adoption studies) suggest that genes are largely responsible for this familial aggregation. We review these studies, including the magnitude of familial risk and heritability estimates, efforts to identify familial subtypes of bipolar disorder, and the implications of family/genetic data for validating nosologic boundaries. Taken together, these studies indicate that bipolar disorder is phenotypically and genetically complex. © 2003 Wiley-Liss, Inc.