Stress and Depression

Major depressive disorder is a significant contributor to the global burden of disease, and it appears to be a mental disorder that is strongly dependent upon exposure to stressful stimuli. A major concern related to the development of animal models of depression is to capture those variables that explain the much higher incidence of depression in human females compared to males. Several genetically selected animal models have been studied, including the Flinders sensitive strain and the WKY strain. In addition, a strain of rats has been selected that is highly susceptible to the development of learned helplessness. Two especially valuable animal models of depression involve exposure of inbred mice to chronic social defeat stress (CSDS) or to chronic unpredictable mild stress. Results from these animal models point to disruptions in dopamine circuits in the brain as critical for the expression of depressive symptoms.