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Genetic aetiology

Last reviewed dd mmm yyyy. Last edited dd mmm yyyy

Authoring team

There is evidence for the importance of genetics in the aeitology of severe unipolar depression:

  • the risk of severe depression in the first degree relatives of a severely depressed patient is 10-15% (compared to 1-2% in the general population)

The evidence for a genetic aetiology of bipolar disorder is stronger:

  • the concordance in twin studies is:
    • 70% for monozygotic twins reared together
    • 70% for monozygotic twins reared apart
    • 23% for dizygotic twins
  • in adoption studies, risk for bipolar affective disorder stems more from the genetic rather than the adoptive parent

The inheritance is probably non-Mendelian.

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