Twin Studies


Introduction Page Adoption Studies
Description of Bipolar Disorder Association Studies
Genetic Factors in Bipolar Disorder Linkage Studies
Family Studies Reference Page
Twin Studies Bipolar Links on the Web

    Numerous twin studies have been conducted to find that the average concordance rate for bipolar disorder among monozygotic twins is 60% and approximately 12% for dizygotic twins.  Environmental factors must also be responsible to explain why concordance among identical twins is not closer to 100%. (Millon, Blaney, & Davis, 1999)
 
 


In Craddock and Jones (1999) research,  6 studies using the DSM IV criteria for Bipolar Disorder were compiled


 
 
Relationship to Proband 
Risk of Bipolar Disorder
Risk of Unipolar Depression
Monozygotic Co-twin 
40-70% 
15-25%
First Degree Relative 
5-10% 
10-20%
General Population 
 0.5-1.5% 
 5-10%

 
 
 
 
 

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