Rethinking Resting Heart Rate Variability: No Evidence of Association With Self-Regulation and Psychopathology in a Cross-Sectional Study Among Adolescents in Colombia, Nepal, and South Africa.

Resting-state heart rate variability (HRV) has been proposed by some researchers as a potential transdiagnostic measure of psychopathology. It is often found to be reduced across a range of mental health conditions and is thought to reflect self-regulatory processes, which are often impaired in these conditions. However, most existing evidence is derived from high-income countries with limited ethnic variation. This leaves a critical gap in understanding whether these associations generalize to low- and middle-income countries (LMICs) or to individuals from under-represented ethnic backgrounds. In this cross-sectional study, we examined the relationship between resting-state HRV, self-regulation, and psychopathology in a large, diverse sample of 1107 adolescents aged 13-15 years living in urban poverty across Colombia, Nepal, and South Africa. We tested seven pre-registered hypotheses across two domains: self-regulation (emotional regulation, inhibitory control, and delay discounting) and psychopathology (anxiety, depression, externalizing symptoms). We used linear mixed models for the confirmatory analyses and complemented them with exploratory equivalence testing. Contrary to our hypotheses based on the neurovisceral integration (NVI) model, HRV was not significantly associated with any outcomes, except for a small effect on externalizing behavior in the opposite direction of our hypothesis. Equivalence testing further indicated that the observed estimates were statistically equivalent, which suggests a meaningful effect is absent. These findings challenge the assumption that HRV-psychological associations are universal and point to the importance of considering contextual, cultural, developmental, and methodological factors in psychophysiological research. This study aims to contribute to a broader rethinking of HRV's role in mental health research, especially in populations that have been under-represented in the literature.