Bipolar disorder (BD) is a serious psychiatric disorder affecting around 1% of the population worldwide. While medications are indispensable for these patients, they are not completely effective, and the underlying genetic architecture and pathogenesis of BD remain unresolved. Researchers from Japan have now used deep exome sequencing to show that mosaic variants/mutations found in genes related to developmental disorders and autism spectrum disease and in the mitochondrial tRNA region could be associated with BD.