BDNF and depressive symptom measurement: A selective deletion of the BDNF‐encoding gene within the mouse dentate gyrus also results in a reduction in antidepressant efficacy (Adachi, Barrot, Autry, Theobald, & Monteggia, 2008) and, conversely, the infusion of BDNF into the lateral cerebral ventricle (Hoshaw, Malberg, & Lucki, 2005) or the dorsal hippocampus (Shirayama et al., 2002) elicits antidepressant effects in behavioral models of depression.