Bipolar disorder (BD) is a common psychiatric
disorder with a lifetime prevalence of approximately 1%. It is characterized by mood swings between positive
manic/hypomanic and negative/depressive states.
Although epidemiological studies indicate that genetic components contribute to BD development, several genome-wide association studies (GWASs) identified limited number of susceptibility (risk) genes for BD, most of which are yet unidentified.
Collaborative research in Japan, under the guidance of the principle investigators from Fujita Health University and RIKEN, led to the identification of a novel risk gene (FADS1 and FADS2) for bipolar disorder via GWAS performed using samples collected in Japan (2,964 cases and 61,887 comparison subjects).
To maximize the sample size, the researchers then conducted a meta-analysis between their samples and results from the publicly available BD GWAS database (Psychiatric GWAS Consortium). They identified an additional novel gene for BD (NFIX) and supported three previously implicated genes (ODZ4, MAD1L1, and TRANK1).
The sample size analyzed in this study is one of the largest, especially as samples were collected in Asian populations. However, because of the extremely small effect size of the BD risk (i.e., odds ratio ~1.2), Prof. Nakao Iwata says, "a large number of risk genes are still unidentified. Therefore further study is essential."
In addition, he says, "We cannot use this information in the clinical setting yet. After elucidating a concrete association of these genes with BD, in terms of their function, new therapeutic strategies may be developed, including the development of new drugs."