Studying the genetics of mood disorders has never been more exciting. We have moved rapidly from establishing the genetic basis of depression to asking questions about how genes are expressed. This has been made possible by the capacity to collect and sequence DNA for large samples cheaply. But "multidisciplinary" approaches investigating interrelationships between risk factors have also been increasingly adopted, encouraging collaborations between those studying genes and those studying the brain, cognition, and/or the social environment. In this review, we first describe findings from quantitative and molecular studies investigating the genetic basis of depression. Second, we present overviews of three hot topics of genetic research: gene-environment interplay, which considers how genetic factors shape exposure and responses toward the social environment; endophenotypic research, which identifies neurophysiological and psychological mediators of genetic risk; and epigenetics, which explain how early environments can foster changes in gene expression, altering subsequent emotional development.