In both animal models and human studies, maternal stress, defined broadly to include illicit drug exposures, tobacco smoking, anxiety, and depression, and their accompanying physiologic responses has been linked to the downregulation of placental HSD11B2 gene expression, and accompanying increased fetal exposure to cortisol [16], [17], [22], [23], [24], [25]. The gene discussed is HSD11B2; the disease is major depressive disorder.