Posted by jrbecker on May 13, 2003, at 15:29:15
The study below answers the question I've always asked myself - "if you have bipolar relatives, does that mean your depression is necessarily bipolar in nature as well?" According to this study, it most likely does...
http://archpsyc.ama-assn.org/cgi/content/abstract/60/5/497
The Heritability of Bipolar Affective Disorder and the Genetic Relationship to Unipolar Depression
Peter McGuffin, MB, PhD, FRCP, FRCPsych; Fruhling Rijsdijk, PhD; Martin Andrew, MB, MRCPsych; Pak Sham, BM, PhD, MRCPsych; Randy Katz, PhD; Alastair Cardno, MB, PhD, MRCPsych
Arch Gen Psychiatry. 2003;60:497-502.Background Twin studies of bipolar affective disorder (BPD) have either been small or have not used explicit diagnostic criteria. There has been little use of genetic model fitting and no analyses to explore the etiological overlap with unipolar depression (UPD).
Methods Sixty-seven twin pairs, 30 monozygotic and 37 dizygotic, in which the proband had BPD were ascertained, and lifetime diagnoses were made using DSM-IV criteria. Univariate models were applied to estimate the contribution of additive genetic and environmental effects. Bipolar data were then combined with those from 68 monozygotic and 109 dizygotic pairs in which the proband had UPD. Two models were explored: a classic 2-threshold approach, in which BPD and UPD occupy the same continuum of liability but differ in severity, and a correlated liability model of mania and depression.
Results Heritability of BPD was estimated at 85% (95% confidence interval [CI], 0.73-0.93) using narrow concordance and 89% (95% CI, 0.61-1.0) using broad concordance, with no shared environmental effects detected. A 2-threshold model was an unsatisfactory fit. Fitting a correlated liability model revealed a genetic correlation of 0.65 (95% CI, 0.58-0.75) between mania and depression and a correlation of 0.59 (95% CI, 0.15-0.84) for nonfamilial environment. Approximately 71% of the genetic variance for mania was not shared with depression.
Conclusions As defined by the DSM-IV, BPD is highly heritable. There are substantial genetic and nonshared environmental correlations between mania and depression, but most of the genetic variance in liability to mania is specific to the manic syndrome.
From the Social, Genetic, and Developmental Psychiatry Centre, Institute of Psychiatry, King's College London, London, England (Drs McGuffin, Rijsdijk, and Sham); the Department of Psychological Medicine, University of Wales College of Medicine, Cardiff (Drs Andrew and Cardno); and the Department of Psychology, Toronto University, Toronto, Ontario (Dr Katz).
poster:jrbecker
thread:226374
URL: http://www.dr-bob.org/babble/20030505/msgs/226374.html