LEP and obesity due to melanocortin 4 receptor deficiency: The association of mood disorders with obesity has been replicated in several rodent models, and proposed pathophysiological mechanisms for the connection include excessive production of proinflammatory cytokines that indirectly affect serotonin production9, elevated leptin levels acting on leptin receptors in the brain10, neuroinflammation as an extension of the systemic inflammation that commonly accompanies obesity11, and high fat diet-induced alterations in glucocorticoid signaling in the hippocampus12.