INSR and major depressive disorder: These neuropathologies and other chronic mental disorders such as schizophrenia (2) and major depressive disorder (MDD) have different etiologies but share common pathogenic manifestations such as neuroinflammation (3), brain glucose hypometabolism (4), oxidative stress (5), mitochondrial dysfunction (6), amyloidosis (7), insulin resistance (8, 9), and/or molecular alterations regarding insulin receptors and the insulin-induced signal transduction pathway (10) (Figure 1).