Chronic use of multiple mild stressors is a model of animal depression, as animals tend to develop symptoms of learned helplessness over the course of days and weeks. Mild stressors commonly used include cold-water swim, immobilization, social isolation, food and water deprivation, chronic illumination, white noise exposure, tail pinch, tilted or shaken cage, and electric shock, although experiments typically do not use all of the above. Multiple mild stressors decrease cell proliferation directly following a stressor, although this effect can be short-lived (Xu et al., 2007). Neurons born prior to mild stressor exposure show diminished differentiation and survival (Lee et al., 2006; Oomen et al., 2007). Overall, the results suggest that chronic stressful experience decreases adult neurogenesis by influencing cell proliferation, neuronal differentiation and cell survival although the effects vary depending on the study perhaps because of differences in stressor, species or strain.
