BDNF and major depressive disorder: Some other candidate genes included FKBP5 (a co-chaperone to glucocorticoid receptors as part of the HPA axis leading to stress response regulation and anxiety); the gene encoding the brain-derived neurotrophic factor, BDNF (hypothesized role in mood disorders; Nugent et al., 2011); and the oxytocin receptor gene, OXTR (oxytocin receptors are concentrated in the hypothalamus and dysregulation has been associated with depression and anxiety).