The heritability of mental disorders is high, but it has been very difficult to unravel the genetic architecture. In the past five years, unprecedented progress has been made on the insight of the genetic background of several mental disorders, and the present article describes the current results. The disorders are extremely polygenic with thousands of common as well as rare risk variants, some of which are shared across disorders. Epigenetic modifications and potentially gene-environment interactions are adding further complexity to the picture.