Childhood adversity and vagal regulation: A systematic review and meta-analysis.

Childhood adversity (CA) is associated with increased risk for physical and mental health problems, with alterations in vagal regulation (an aspect of autonomic functioning indexed by vagally-mediated heart rate variability [vmHRV]) implicated as a mechanism. Three-level meta-analyses were conducted to synthesize research on the relationship between CA and 1) baseline vagal activity, and 2) vagal reactivity to challenges including stress tests, emotion-eliciting tasks and cognitive tasks. No significant overall association was found between CA and vagal activity (r = -.015; p = .11) or vagal reactivity (r = -.017; p = .13). However, analyses controlling for moderator interrelatedness revealed an association between CA and lower baseline vagal activity in samples including participants diagnosed with a psychiatric disorder, and for direct adversities such as maltreatment. For vagal reactivity, CA was associated with lower reactivity if the adversity was experienced less recently, and for studies operationalizing reactivity using task mean levels of vmHRV. These findings indicate that small alterations in vagal functioning occur for specific CA subtypes and subgroups of individuals.