Described herein are assays, kits and methods for treating mood disorders by testing for one or more polymorphisms in a specific group of genes and for analyzing the results of polymorphism testing; the genes included may converge in one or more signaling pathways, and may be epigenetic. The genes are included based on the relationships of the proteins encoded by the genes in the context of particular signaling pathways and provide a diagnostically relevant nexus. Also described herein are methods of presenting the data collected by the screen, including methods of delivering interpretive comments and/or treatment guidance based on the results of the genetic screening either individually or based on the genetic composition of particular clusters of genes which may be related to each other. Importantly, drugs which modulate these genetic disturbances are described for targeted therapeutic use based upon companion diagnostic method.