BDNF and major depressive disorder: In animal models, inhalation of basil essential oil has been found to increase serum glucocorticoid levels, reduce neuronal and glial apoptosis, enhance neurogenesis in the dentate gyrus [35], decrease the expression of glucocorticoid receptor and brain-derived neurotrophic factor (BDNF) genes and proteins in the hippocampus, and alleviate depression induced by unpredictable mild stress [36].