axis, but also influences the development of the stress- and threat-response systems. Inadequate or disorganized parental care influences stress system hyperreactivity to stressors that might persist throughout life and influences hyper-defensive behavior. These parenting effects are produced, at least in part, through epigenetic processes (i.e., methylation of the glucocorticoids receptor gene in negative feedback pathways of the L-HPA system; Meaney and Szyf, 2005). In addition, there is increasing evidence that CRH, in synergy with GCs, mediates some of these parenting effects (Brunson et al., 2001). Early adverse parental care also increases CRH-1 receptor expression in limbic and cortical regions, thus increasing sensitivity to the fear-/stress-organizing effects of CRH over time (Sanchez et al., 2001). In Figure 1, we have depicted the importance of caregiving, with the close spacing of the arrows from the caregiving box indicating the high dependence of infant mammals on parental support and the decreasing, but still evident, dependence on such support with development.
