When the organism continues to be exposed to stress and exceeds the limit of adaptive adjustment, the LH-LC MCH innervation re-increased, accompanied by a decrease in MCHR1 expression and a recurrence of depression-like behaviors, such a strong correlation indicating chronic stress-induced abnormalities of the MCHergic system may be one of the important factors for depression-like behaviors. Here, MCHR1 is linked to major depressive disorder.