Bipolar disorder is a severe mental disorder characterized by episodes of mania and depression. The heritability is estimated to be up to 80% in epidemiological studies. Parts of the variance is explained by common single nucleotide polymorphisms, and ongoing international consortia collect tens of thousands of patients to find the associated variants. So far, genome-wide association studies have found 64 significant loci with enrichment of genes involved in calcium signaling and synaptic structures. It is not known how these variants lead to disease, but studies are ongoing. One way to estimate the complete genetic risk is by calculating polygenic risk scores. Multiple studies have sought to unravel the polygenic architecture of bipolar disorder by associating various subphenotypes in bipolar patients with genetic risks for other disorders and traits.