The Association between Adversity and Hair Cortisol Levels in Humans: A Meta-Analysis

• In Event: 1-131 - Blunted Versus Elevated Hair Cortisol: Differential Relations to Developmental and Intergenerational Predictors and Outcomes

Integrative Statement

Introduction: Adverse life events are associated with a constellation of negative health outcomes. Theory and research have suggested that the hypothalamic-pituitary-adrenal (HPA) axis acts as one mechanism connecting adverse experiences with the development of health difficulties. Over the past decade, methodological advances have enabled the sampling of cortisol in hair, providing a retrospective marker of chronic stress. However, the direction of association between adversity and cortisol levels has varied, with some studies suggesting that those who have experienced adversity have elevated hair cortisol (Simmons et al., 2016), while other studies have reported lower hair cortisol (White et al., 2017). The present meta-analysis provides a quantitative synthesis and review of the adversity and hair cortisol literature to elucidate the HPA axis outcomes associated with adversity.

Aims/Hypotheses: The first aim of the present meta-analysis was to systematically summarize and quantify the strength of the relation between adversity and hair cortisol. Given the inherent complexities of how the HPA axis responds to chronic stress, we hypothesized that the effects of adversity on hair cortisol varies in direction. We further aimed to explore the potential causes of this variation. Thus, the second aim of the meta-analysis was to explore participant and methodological characteristics that moderate the strength and direction of relations between adversity and hair cortisol.

Methods: We conducted a comprehensive search on several databases (PsycINFO, MEDLINE, Social Science Index, EMBASE, Dissertation Abstract International; see Figure 1 for study inclusion process) and identified 26 studies that met inclusion criteria. We examined a range of adversity classes, including childhood maltreatment, domestic violence, and exposure traumas (e.g., accidents, war, natural disasters). We explored several variables associated with article publication (e.g., publication year, publication status), sample characteristics, hair cortisol measurement, and assessment of adversity. Analyses were conducted using Comprehensive Meta-Analysis (CMA; Version 3.0) software.

Results: When differences in the direction of effect were combined, the overall effect size of adversity on hair cortisol across all studies was small, d = 0.14 [-0.02, 0.30]. However, in the 18 studies that produced positive effects, the overall effect size was medium (d = 0.36, [0.22, 0.50]); and in the 8 studies that produced a negative effect, the effect size was also medium (d = -0.50, [-0.76, -0.24]). Moderators that affected the strength and direction of the association between adversity and hair cortisol included features of adversity measurement (i.e., type of adversity, timing of adversity, specific adversity measure utilized), features of hair samples (i.e., length of sample, hair washing, length of time between adversity exposure and hair sampling), and characteristics of the samples (i.e., age group, racial distribution).

Conclusions: Overall, findings indicated that adversity significantly affects hair cortisol, with the direction and magnitude of effects varying greatly. However, the major gap in the literature is the lack of studies examining the relation between adversity and HCC in childhood. These findings further our knowledge of the long-term impact of adversity on the dysregulation of the HPA axis and inform future directions for hair cortisol research.

Authors

• Jennifer Khoury, Harvard Medical School, Cambridge Hospital
  Presenting Author

• Michelle Bosquet Enlow, Boston Children's Hospital and Harvard Medical School
  Non-Presenting Author

• Karlen Lyons-Ruth, Cambridge Health Alliance and Harvard Medical School
  Non-Presenting Author