The genetic basis of bipolar disorder

The high heritability of bipolar disorder (BD) means that a full understanding of etiology must account for the strong influence of inherited genetic variation. An energetic search for specific genetic risk factors over the past 25 years has begun to bear fruit, but most of the genetic risk for BD remains unexplained. In this chapter, we will review the genetic epidemiology of BD, studies aimed at identifying genes that confer risk for the illness, functional genomic studies that seek to elucidate the pathophysiology of BD from the level of genes and gene networks, and pharmacogenomic studies that aim to identify genetic markers of treatment outcome. We conclude with a view to future directions that may ultimately lead to a more complete understanding of this common, severe mental illness and better approaches to diagnosis and treatment.