[Genetics of bipolar disorder]

Bipolar disorder (BD) has a multifactorial etiology. Its development is influenced by genetic as well as environmental factors. Large genome-wide association studies (GWAS), in which genetic risk allelic variants for the disorder could be replicated for the first time, marked the breakthrough in the identification of the responsible risk genes. In addition to these common genetic variants with moderate effects identified by GWAS, rare variants with a higher penetrance are expected to play a role in disease development. The results of recent studies suggest that copy number variants might contribute to BD development, although to a lesser extent than in other psychiatric disorders, such as schizophrenia or autism. Results from the initial next generation sequencing studies indicate an enrichment of rare variants in pathways and genes that were previously found to be associated with BD. In the field of pharmacogenetics, a risk gene that influences the individual variance in the response to lithium treatment was identified for the first time in a recent large international GWAS. Currently the reported risk alleles do not sufficiently explain the phenotypic variance to be used for individual prediction of disease risk, disease course or response to medication. Future genetic research will provide important insights into the biological basis of BD by the identification of additional genes associated with BD. This knowledge of genetics will help identify potential etiological subgroups as well as cross-diagnostic disease mechanisms.