In addition, Pb can contribute to the development of mental disorders (especially depression) through mechanisms causing irregularities in the serotonergic system (5-HT), hypothalamic–pituitary–adrenal (HPA) axis dysregulation, and an increase in corticotropin-releasing hormone (CRH) and cortisol levels [39,40,41,42]. This evidence concerns the gene CRH and psychiatric disorder.