Given the previous finding that X-irradiation of a restricted region of the mouse brain containing the hippocampus inhibited the neurogenic and anxiety-related behavioral effects of two classes of antidepressants, suggesting that the behavioral effects of chronic antidepressant use were mediated by the stimulation of neurogenesis in the hippocampus [23], we next examined whether neurogenesis is accelerated in the adult hippocampus of Tdo-/- mice. Here, TDO2 is linked to Anxiety.