Early-life stress (ELS), a complex traumatic stress including abuse, neglect and bullying during childhood or adolescence, is closely related to the development of psychiatric disorders. Conduct of a prospective study on the effect of ELS in human subjects is difficult due to ethical issues and limitations, and animal model study can be a reasonable alternative. Articles regarding structural and functional changes in the animal brain associated with ELS have been reviewed in this study. An up-to-date literature search on the effect of ELS on animal brain was performed ; keywords included ELS, central nervous system (CNS), and animal study using PubMed. A total of 623 articles were found and important articles were reviewed. First, we summarized the neurobiological changes in CNS associated with ELS, and then the effects of ELS on emotional and cognitive function and behavioral characteristics were recapped. ELS can induce overreactivity of the hypothalamus-pituitary-adrenal axis and cortical-subcortical structural changes including prefrontal cortex, hippocampus, and amygdala. These changes may be associated with neuroendocrine, cognitive, and emotional dysfunctions and related behavioral changes. Although most animal model studies used a single mode of stress, ELS tends to be experienced with complex types in human-life. Design of a new animal model examining the effects of complex trauma during early-life is important. Studies on the association between complex trauma and brain development can provide important insights regarding the pathogenetic mechanism of complex psychiatric disorders such as personality disorder and treatment-resistant depression.
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