Mental disorders are debilitating conditions that significantly impair the function of the central nervous system and degrade the quality of life. About one-quarter of adult Americans are diagnosed with mental disorders such as major depression, anxiety, and schizophrenia [1
]. Understanding the neurobiological basis of mental disorders, determining effective treatments, and alleviating the respective symptoms are major forces driving modern psychiatry today.
The hippocampus, an area of the brain important in memory, cognitive function, and mood regulation, is particularly vulnerable to chronic stress and mental disorders [2
]. Several landmark clinical studies have demonstrated that major depression is accompanied by a decrease in the volume of hippocampus and consequent deficits in hippocampal function [4
]. Similarly, in schizophrenic patients, shape deformations, cell loss, and volume reduction in the hippocampus were found using neuroimaging analysis [6
]. Reversal of these alterations has successfully improved the behavioral and cognitive symptoms associated with these disorders. Such evidence has encouraged consideration of whether improving hippocampal structure and function could be a potential therapeutic target in treating mental disorders [9
Since the pioneering discovery of mammalian postnatal neurogenesis in the 1960s [58
], adult neurogenesis has been unambiguously investigated in discrete brain regions across mammals including humans. Adult neurogenesis in all mammals, including humans, occurs throughout life within two specialized neurogenic niches, the subventricular zone (SVZ) of the lateral ventricle and the subgranular zone (SGZ) of the hippocampal dentate gyrus [59
]. In particular, adult neurogenesis in dentate gyrus has attracted interest since newborn neurons contribute to enhanced neural plasticity that could sustain specific brain functions such as spatial learning, pattern discrimination, and mood regulation [47
]. In addition, adult hippocampal neurogenesis in the mature brain represents a striking example of activity-dependent neural plasticity such as stress, antidepressants, and brain injuries [62
]. Extensive studies have shown that voluntary exercise, enriched environments, and antidepressants contribute to overall brain health by robustly promoting adult hippocampal neurogenesis [37
]. Decreased neurogenesis in the hippocampus via aging or stress has been implicated in the pathogenesis of cognitive deficits, anxiety and depression [64
]. In fact, adult hippocampal neurogenesis not only plays an important role in antidepressant action [47
] but also plays a role in ameliorating various pathological disease conditions [25
]. Therefore, a better understanding of the molecular and cellular mechanisms that regulate adult hippocampal neurogenesis may offer new therapeutic targets.
In this paper, we will highlight three major psychiatric disorders that have been associated with adult hippocampal neurogenesis. We will present and interpret the significance of the results in regards to the mechanism of cognitive and neurological disorders. Finally, we will lay out some current and potential therapeutic treatments that are used to counter these psychiatric disorders.