Chronic stress paradigms typically utilize daily stressors over the course of a few days to several weeks. Chronic social stress decreases cell proliferation in tree shrews (Czeh et al., 2001; Czeh et al., 2002; Simon et al., 2005), rats (Czeh et al., 2007), and mice (Ferragud et al., 2010), where subordinate behavior is negatively correlated with cell proliferation rates (Mitra et al., 2006). Chronic social stress also decreases differentiation of new neurons in mice (Ferragud et al., 2010), although this may reflect changes in proliferation, and survival of new neurons in tree shrews (Czeh et al., 2002) and rats (Czeh et al., 2007). Chronic restraint stress has been shown to decrease or not change cell proliferation in adult rats (Pham et al., 2003; Rosenbrock et al., 2005). Chronic restraint stress has also been shown to reduce survival of new neurons in rats (Pham et al, 2003) but enhance survival of new neurons in mice (Snyder et al., 2009b). Chronic electric shock decreases both cell proliferation and neuronal differentiation (although this latter effect may stem from reduced cell proliferation as well) in adult rats (Dagyte et al., 2009).
