Professional Education


  • Bachelor of Science, Vanderbilt University (2005)
  • Doctor of Philosophy, University of California Los Angeles (2014)
  • Master of Education, Harvard University (2006)

Stanford Advisors


All Publications


  • The impact of the severity of early life stress on diurnal cortisol: The role of puberty. Psychoneuroendocrinology King, L. S., Colich, N. L., LeMoult, J., Humphreys, K. L., Ordaz, S. J., Price, A. N., Gotlib, I. H. 2017; 77: 68-74

    Abstract

    Researchers have documented dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis in children and adolescents who experienced early life stress (ELS). The precise nature of this dysregulation, however, has been difficult to discern. In fact, both elevated and blunted patterns of diurnal cortisol regulation have been reported in children and adolescents exposed to greater ELS, including both reduced and heightened cortisol levels and change in cortisol across the day. These divergent findings may be due to developmental changes in the relation between ELS and HPA-axis functioning. The present study was designed to examine the role of puberty in the impact of the severity of ELS on the regulation of diurnal cortisol. Boys and girls (N=145) ages 9-13 years recruited from lower-risk communities completed an interview about their ELS experiences and at-home collection of diurnal cortisol. ELS experiences were objectively coded for severity, and children's level of pubertal development was measured using Tanner Staging. Multi-level piecewise mixed-effects models tested the effects of ELS severity and pubertal stage on cortisol levels at waking, the cortisol awakening response (CAR), and the daytime cortisol slope. While we found no significant interactive effects of pubertal stage and ELS severity on cortisol levels at waking or the daytime cortisol slope, findings indicated that pubertal stage interacted with ELS severity to predict the cortisol awakening response (CAR). Specifically, in earlier puberty, higher ELS was associated with a blunted CAR compared to lower ELS; in contrast, in later puberty, higher ELS was associated with a heightened CAR compared to lower ELS. Differences in the relation between ELS severity and the CAR were uniquely determined by puberty, and not by age. By considering and examining the role of puberty, the current study provides a developmental explanation for previous divergent findings of both blunted and heightened patterns of diurnal cortisol following ELS. These results indicate that careful attention should be given to children's pubertal status before drawing conclusions concerning the nature of diurnal cortisol dysregulation.

    View details for DOI 10.1016/j.psyneuen.2016.11.024

    View details for PubMedID 28024271

  • Attentional avoidance of fearful facial expressions following early life stress is associated with impaired social functioning. Journal of child psychology and psychiatry, and allied disciplines Humphreys, K. L., Kircanski, K., Colich, N. L., Gotlib, I. H. 2016; 57 (10): 1174-1182

    Abstract

    Early life stress is associated with poorer social functioning. Attentional biases in response to threat-related cues, linked to both early experience and psychopathology, may explain this association. To date, however, no study has examined attentional biases to fearful facial expressions as a function of early life stress or examined these biases as a potential mediator of the relation between early life stress and social problems.In a sample of 154 children (ages 9-13 years) we examined the associations among interpersonal early life stressors (i.e., birth through age 6 years), attentional biases to emotional facial expressions using a dot-probe task, and social functioning on the Child Behavior Checklist.High levels of early life stress were associated with both greater levels of social problems and an attentional bias away from fearful facial expressions, even after accounting for stressors occurring in later childhood. No biases were found for happy or sad facial expressions as a function of early life stress. Finally, attentional biases to fearful faces mediated the association between early life stress and social problems.Attentional avoidance of fearful facial expressions, evidenced by a bias away from these stimuli, may be a developmental response to early adversity and link the experience of early life stress to poorer social functioning.

    View details for DOI 10.1111/jcpp.12607

    View details for PubMedID 27457566

  • DNA methylation at stress-related genes is associated with exposure to early life institutionalization AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY Non, A. L., Hollister, B. M., Humphreys, K. L., Childebayeva, A., Esteves, K., Zeanah, C. H., Fox, N. A., Nelson, C. A., Drury, S. S. 2016; 161 (1): 84-93

    Abstract

    Differences in DNA methylation have been associated with early life adversity, suggesting that alterations in methylation function as one pathway through which adverse early environments are biologically embedded. This study examined associations between exposure to institutional care, quantified as the proportion of time in institutional care at specified follow-up assessment ages, and DNA methylation status in two stress-related genes: FKBP5 and SLC6A4.We analyzed data from the Bucharest Early Intervention Project, which is a prospective study in which children reared in institutional settings were randomly assigned (mean age 22 months) to either newly created foster care or care as usual (to remain in their current placement) and prospectively followed. A group of children from the same geographic area, with no history of institutionalized caregiving, were also recruited. DNA methylation status was determined in DNA extracted from buccal epithelial cells of children at age 12.An inverse association was identified such that more time spent in institutional care was associated with lower DNA methylation at specific CpG sites within both genes.These results suggest a lasting impact of early severe social deprivation on methylation patterns in these genes, and contribute to a growing literature linking early adversity and epigenetic variation in children. Am J Phys Anthropol 161:84-93, 2016.. © 2016 Wiley Periodicals, Inc.

    View details for DOI 10.1002/ajpa.23010

    View details for Web of Science ID 000383549400009

    View details for PubMedID 27218411

  • Impaired Social Decision-Making Mediates the Association Between ADHD and Social Problems JOURNAL OF ABNORMAL CHILD PSYCHOLOGY Humphreys, K. L., Galan, C. A., Tottenham, N., Lee, S. S. 2016; 44 (5): 1023-1032

    Abstract

    Attention-deficit/hyperactivity disorder (ADHD) reliably predicts social dysfunction, ranging from poor social competence and elevated peer rejection to inadequate social skills. Yet, the factors mediating predictions of social problems from childhood ADHD are not well understood. In the present study, we investigated social functioning in 186 (69 % male) 6 to 10 year-old (M = 7.88, SD = 1.17) children with (n = 98) and without (n = 87) ADHD who were followed prospectively for two years. We implemented a well-validated measure of social problems as well as a novel social decision-making task assessing dynamic response to changing affective cues at the two-year follow-up. According to separate parent and teacher report, baseline ADHD symptoms positively predicted social problems at the two-year follow-up; individual differences on the social decision-making task mediated this association. This finding was replicated when ADHD dimensions (i.e., inattention and hyperactivity/impulsivity) were separately examined. These findings suggest that the deficient use of affective cues to effectively guide behavior may partially underlie poor social functioning among children with ADHD. If replicated, these preliminary findings suggest that social skills interventions that target interpretation of affective cues to aid in social decision-making behavior may improve social outcomes negatively affected by early ADHD symptoms.

    View details for DOI 10.1007/s10802-015-0095-7

    View details for Web of Science ID 000377449600016

    View details for PubMedID 26486935

  • Previous Institutionalization Is Followed by Broader Amygdala-Hippocampal-PFC Network Connectivity during Aversive Learning in Human Development JOURNAL OF NEUROSCIENCE Silvers, J. A., Lumian, D. S., Gabard-Durnam, L., Gee, D. G., Goff, B., Fareri, D. S., Caldera, C., Flannery, J., Telzer, E. H., Humphreys, K. L., Tottenham, N. 2016; 36 (24): 6420-6430

    Abstract

    Early institutional care can be profoundly stressful for the human infant, and, as such, can lead to significant alterations in brain development. In animal models, similar variants of early adversity have been shown to modify amygdala-hippocampal-prefrontal cortex development and associated aversive learning. The current study examined this rearing aberration in human development. Eighty-nine children and adolescents who were either previously institutionalized (PI youth; N = 46; 33 females and 13 males; age range, 7-16 years) or were raised by their biological parents from birth (N = 43; 22 females and 21 males; age range, 7-16 years) completed an aversive-learning paradigm while undergoing functional neuroimaging, wherein visual cues were paired with either an aversive sound (CS+) or no sound (CS-). For the PI youth, better aversive learning was associated with higher concurrent trait anxiety. Both groups showed robust learning and amygdala activation for CS+ versus CS- trials. However, PI youth also exhibited broader recruitment of several regions and increased hippocampal connectivity with prefrontal cortex. Stronger connectivity between the hippocampus and ventromedial PFC predicted significant improvements in future anxiety (measured 2 years later), and this was particularly true within the PI group. These results suggest that for humans as well as for other species, early adversity alters the neurobiology of aversive learning by engaging a broader prefrontal-subcortical circuit than same-aged peers. These differences are interpreted as ontogenetic adaptations and potential sources of resilience.Prior institutionalization is a significant form of early adversity. While nonhuman animal research suggests that early adversity alters aversive learning and associated neurocircuitry, no prior work has examined this in humans. Here, we show that youth who experienced prior institutionalization, but not comparison youth, recruit the hippocampus during aversive learning. Among youth who experienced prior institutionalization, individual differences in aversive learning were associated with worse current anxiety. However, connectivity between the hippocampus and prefrontal cortex prospectively predicted significant improvements in anxiety 2 years following scanning for previously institutionalized youth. Among youth who experienced prior institutionalization, age-atypical engagement of a distributed set of brain regions during aversive learning may serve a protective function.

    View details for DOI 10.1523/JNEUROSCI.0038-16.2016

    View details for Web of Science ID 000379015300007

    View details for PubMedID 27307231