Do impairments in neurogenesis contribute to the cellular changes observed in mood disorders?
The preceding discussion has centered largely around the possibility that the regional reductions in cell numbers observed in mood disorders is primarily due to cell death. However, the demonstration that neurogenesis occurs in the human brain into senescence,100 raises the possibility that ongoing impairment of neurogenesis may also play a role. The greatest density of new cell birth is observed in the subventricular zone and the subgranular layer of the hippocampus, although a recent study has suggested that new neurons originating from the subventricular zone are found also in areas of association cortex of nonhuman primates.101 Recent studies have shown that decreased neurogenesis occurs in response to both acute and chronic stress, effects which appear to be mediated by glucocorticoids.102 Thus, it is an interesting possibility that the reduced hippocampal volumes that have been observed in conditions associated with elevated glucocorticoid levels (eg MDD, Cushing’s, PTSD) may be
