BDNF/TrkB signaling is well known to be involved in several aspects of behavior, including hippocampal learning and memory (reviewed in Tyler et al.57) and mood.58,59 One potential significant mechanism through which neurotrophic signaling might influence both memory and mood is through modulation of hippocampal neurogenesis, which has been extensively linked to aspects of memory formation, depression, and other behaviors (reviewed in Anacker et al.60). This evidence concerns the gene BDNF and major depressive disorder.