The differential calibration of the HPA axis as a function of trauma versus adversity: A systematic review and p-curve meta-analyses

Although there is an abundance of evidence linking the function of the hypothalamic-pituitary-adrenal (HPA) axis to adverse early-life experiences, the precise nature of the association remains unclear. Some evidence suggests early-life adversity leads to cortisol hyper-reactivity, while other evidence suggests adversity leads to cortisol hypo-reactivity. Here, we distinguish between trauma and adversity, and use p-curves to interrogate the conflicting literature. In Study 1, trauma was operationalized according to DSM-5 criteria; the p-curve analysis included 68 articles and revealed that the literature reporting associations between trauma and blunted cortisol reactivity contains evidential value. Study 2 examined the relationship between adversity and cortisol reactivity. Thirty articles were included in the analysis, and p-curve demonstrated that adversity is related to heightened cortisol reactivity. These results support an inverted U-shaped function relating severity of adversity and cortisol reactivity, and underscore the importance of distinguishing between trauma and adversity.

Automated summary

There is conflicting evidence on whether early-life adversity leads to increased or decreased cortisol reactivity. P-curve analysis revealed that trauma is associated with blunted cortisol reactivity, while adversity is linked to heightened cortisol reactivity. This suggests an inverted U-shaped relationship between severity of adversity and cortisol reactivity.