Bipolar Disorder Candidate Genes

While many genes and loci have subsequently been found to associate with bipolar disorder, none have been unambiguously identified as causal.

We know from family and twin studies that bipolar is a highly genetic disorder. A study of 11,288 same-sex twin pairs in Denmark by Bertelsen and colleagues (1977) found that approximately 58% of monozygotic (identical) twins were concordant for bipolar disorder, as compared with 17% of dizygotic (fraternal) twins. While many genes and loci have subsequently been found to associate with bipolar disorder, none have been unambiguously identified as causal. One explanation for the difficulty in finding genes for bipolar is that it is a highly complex disorder. Genes with the strongest association are also candidate genes for schizophrenia (in particular), as well as major depression. This is not surprising given that the disorders share some common symptoms. For example, psychosis is a feature of both bipolar and schizophrenia (although the delusions and hallucination in schizophrenia seem to be related to self-awareness as opposed to mood-incongruence). Candidate genes for bipolar disorder include G72/DAOA, DISC1, NRG1, TPH2, BDNF, 5-HTT, and DAT1.