High concordance of bipolar I disorder in a nationwide sample of twins

Am J Psychiatry. 2004 Oct;161(10):1814-21. doi: 10.1176/ajp.161.10.1814.


Objective: The few studies of bipolar I disorder in twins have consistently emphasized the genetic contribution to disease liability. The authors report what appears to be the first twin study of bipolar I disorder involving a population-based twin sample, in which the diagnoses were made by using structured, personal interviews.

Method: All Finnish same-sex twins (N=19,124) born from 1940 to 1957 were screened for a diagnosis of bipolar I disorder as recorded in the National Hospital Discharge Register between 1969 and 1991 or self-reported in surveys of the Finnish Twin Cohort in 1975, 1981, and 1990. Thirty-eight pairs were thereby identified and invited to participate in the study; the participation rate was 68%. Lifetime diagnoses were made by using the Structured Clinical Interview for DSM-IV. The authors calculated probandwise and pairwise concordances and correlations in liability and applied biometrical model fitting.

Results: The probandwise concordance rates were 0.43 (95% CI=0.10 to 0.82) for monozygotic twins and 0.06 (95% CI=0.00 to 0.27) for dizygotic twins. The correlations in liability were 0.85 and 0.41, respectively. The model with no familial transmission was rejected. The best-fitting model was the one in which genetic and specific environmental factors explained the variance in liability, with a heritability estimate of 0.93 (95% CI=0.69 to 1.00).

Conclusions: The high heritability of bipolar disorder was demonstrated in a nationwide population-based twin sample assessed with structured personal interviews.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't
  • Twin Study

MeSH terms

  • Adult
  • Bipolar Disorder / diagnosis
  • Bipolar Disorder / epidemiology
  • Bipolar Disorder / genetics*
  • Cohort Studies
  • Diseases in Twins / diagnosis
  • Diseases in Twins / epidemiology
  • Diseases in Twins / genetics*
  • Female
  • Finland / epidemiology
  • Genetic Predisposition to Disease / genetics*
  • Genetic Testing
  • Humans
  • Male
  • Middle Aged
  • Models, Genetic
  • Prevalence
  • Psychiatric Status Rating Scales / statistics & numerical data
  • Psychometrics
  • Registries
  • Risk Factors
  • Sex Factors
  • Social Environment
  • Twins, Dizygotic / genetics
  • Twins, Monozygotic / genetics