In animal models of depression, chronic probiotic administration can reduce anxiety and depressive symptoms and correlates with the normalization of biological indicators of depression, such as corticosterone, noradrenaline, BDNF levels, and cytokines (Desbonnet et al., 2010; Bercik et al., 2011; Bravo et al., 2011). This evidence concerns the gene BDNF and depressive symptom measurement.