Family, twin, and adoption studies of bipolar disease

Abstract

Bipolar disease features states of severe depression that usually fluctuate with at least one episode of intense elation or mania. It is a disorder that has been thought for some time to have a heritable component. The lifetime prevalence of bipolar disease in the general population is approximately 1%. In contrast, family studies have shown the approximate lifetime risk of a first-degree relative of a bipolar proband to be 5% to 10%. Moreover, studies of monozygotic twins show that their risk of contracting the disease is as much as 75 times greater than that for the general population. In addition, adoption studies have demonstrated that biological relatives of bipolar patients are substantially more likely to have the disorder than are adoptive relatives.

Findings in an independent sample support an association between bipolar affective disorder and the G72/G30 locus on chromosome 13q33

“…Adoption studies show that this familiality has a genetic basis, and twin studies demonstrate a high degree of heritability. 1 While a single gene might play a major role in some rare families, multiple genes and environmental factors are usually considered to underlie BPAD susceptibility in most families. Several chromosomal regions have been implicated by genetic linkage and association studies as potential sites of susceptibility loci, 2 but findings have proven difficult to replicate consistently.…”

Genome-wide linkage scan in a large bipolar disorder sample from the National Institute of Mental Health genetics initiative suggests putative loci for bipolar disorder, psychosis, suicide, and panic disorder

“…Family, twin, and adoption studies support a substantial genetic component for BP. 1 Linkage studies, including genome-wide scans, have implicated multiple chromosomal regions as possible sites for susceptibility loci. However, inconsistent results underscore the challenge in attaining compelling findings.…”

Genome-wide scan for genes involved in bipolar affective disorder in 70 European families ascertained through a bipolar type I early-onset proband: supportive evidence for linkage at 3p14

“…1 Family, twin and to a less extent adoption studies strongly support a genetic component of BPAD, buts its mode of inheritance remains unclear. [1][2][3] Genome-wide searches have detected numerous chromosomal regions possibly linked to BPAD, leading to conflicting results. A recent metaanalysis of 18 BPAD genome scan data sets 4 suggested that no chromosomal region achieved genome-wide statistical significance according to several simulation-based criteria.…”