POMC and major depressive disorder: A meta-analysis of studies examining basal and post-challenge HPA axis measures suggests that major depression is associated with only a small to moderate increase in basal cortisol and adrenocorticotropic hormone (ACTH), and a decrease in corticotrophin-releasing hormone (CRH) levels among studies taking into account medication use, diagnostic heterogeneity, and age; while studies not taking these factors into account reported stronger associations between HPA axis function and depression (Stetler and Miller 2011).