Rationale-The investigation of putative effects of early life stress (ELS) in humans on later behavior and neurobiology is a fast developing field. While epidemiological and neurobiological studies paint a somber picture of negative outcomes, relatively little attention has been devoted to integrating the breadth of findings concerning possible cognitive and emotional deficits associated with ELS. Emerging findings from longitudinal studies examining developmental trajectories of the brain in healthy samples may provide a new framework to understand mechanisms underlying ELS sequelae.Objective-The goal of this review was two-fold. The first was to summarize findings from longitudinal data on normative brain development. The second was to utilize this framework of normative brain development to interpret changes in developmental trajectories associated with deficits in cognitive and affective function following ELS.Results-Five principles of normative brain development were identified and used to discuss behavioral and neural sequelae of ELS. Early adversity was found to be associated with deficits in a range of cognitive (cognitive performance, memory, and executive functioning) and affective (reward processing, processing of social and affective stimuli, and emotion regulation) functions. Conclusion-Three general conclusions emerge:(1) higher-order, complex cognitive and affective functions associated with brain regions undergoing protracted postnatal development are particularly vulnerable to the deleterious effects of ELS; (2) the amygdala is particularly sensitive to early ELS; and (3) several deficits, particularly those in the affective domain, appear to persist years after ELS has ceased and may increase risk for later psychopathology.

The amygdala is vulnerable to stress-dependent disruptions in neural development. Animal models have shown that stress increases dendritic arborization leading to larger amygdala volumes. Human studies of early stress and amygdala volume, however, remain inconclusive. This study compared amygdala volume in adults with childhood maltreatment to healthy controls. Eighteen participants from a longitudinal cohort and 33 cross-sectional controls (17M/35F, 25.4 ±3.1 years) completed a structural magnetic resonance imagining scan and the Maltreatment and Abuse Chronology of Exposure scale. Random forest regression with conditional trees was used to assess relative importance of exposure to adversity at each age on amygdala, thalamic or caudate volume. Severity of exposure to adversity across age accounted for 27% of the variance in right amygdala volume. Peak sensitivity occurred at 10–11 years of age, and importance of exposure at this time was highly significant based on permutation tests (p=0.003). The regression model showed that exposure during this sensitive period resulted in steep dose-response function with maximal response to even modest levels of exposure. Subjects in the highest exposure quartile (MACE-11, range 11 – 54) had a 9.1% greater right amygdala volume than subjects in the lowest exposure quartile (MACE-11, < 3.5). No associations emerged between age of exposure and volume of left amygdala or bilateral caudate or thalamus. Severity of adversity experienced at age 10–11 contributed to larger right but not left amygdala volume in adulthood. Results provide preliminary evidence that the amygdala may have a developmental sensitive period in preadolescence.

As a step toward addressing limitations in the current psychiatric diagnostic system, the NIMH recently developed the Research Domain Criteria (RDoC) to stimulate integrative research—spanning self-report, behavior, neural circuitry, and molecular/genetic mechanisms—on core psychological processes implicated in mental illness. Here, we use the RDoC conceptualization to review research on threat responses, reward processing, and their interaction. The first section of the manuscript highlights the pivotal role of exaggerated threat responses—mediated by circuits connecting the frontal cortex, amygdala, and midbrain—in anxiety, and reviews data indicating that genotypic variation in the serotonin system is associated with hyperactivity in this circuitry, which elevates the risk for anxiety and mood disorders. In the second section, we describe mounting evidence linking anhedonic behavior to deficits in psychological functions that rely heavily on dopamine signaling, especially cost/benefit decision-making and reward learning. The third section covers recent studies that document negative effects of acute threats and chronic stress on reward responses in humans. The mechanisms underlying such effects are unclear, but new optogenetic data in rodents indicate that GABAergic inhibition of midbrain dopamine neurons, driven by activation of the habenula, may play a fundamental role in stress-induced anhedonia. In addition to its basic scientific value, a better understanding of interactions between the neural systems that mediate threat and reward responses may offer relief from the burdensome condition of anxious depression.