Background: Psychophysiological hyperresponsiveness to social-evaluative stress plays a key role in current theories of social phobia (SP). Owing to the early onset of this disorder, the study of children with SP can help to improve etiological models. However, research to date has failed to clarify whether children with SP are physiologically hyperresponsive to stress or not. In addition, the existence of elevated pre-stressor baseline group differences complicates the interpretation of acute stress responses and therefore poses a challenge for this line of research. Drawing on current models of autonomic control to explain the relationship between baseline and stress responding in SP children and healthy controls (HC), we acquired a broad set of autonomic measures in our study. Method: To index baseline and stress reactivity and to assess autonomic flexibility, we assessed a comprehensive array of sym-pathetic and parasympathetic measures in SP children (aged 8 to 12 years; n = 30) and healthy control children (HC, n = 26), while exposing them to the Trier Social Stress Test for Children (TSST-C). Results: At baseline, the SP children showed higher levels of sympathetic (heart rate, electrodermal activity) and lower levels of parasympathetic (respiratory sinus arrhythmia, RSA) activation when compared to the HC children. During the TSST-C, the SP children showed similar HR responses but a limited RSA reactivity and a slower HR recovery relative to the HC children. Conclusion: Our study extends previous research by showing elevated baseline arousal and comparable stress responding in SP children relative to HC children. In addition, based on the autonomic flexibility model, we provide a potential explanation for the null findings of previous studies during stress. The pattern of elevated baseline heart rates and reduced RSA point to restricted autonomic flexibility in children with SP.

Abstract The present study is informed by the theory of allostatic load to examine how multiple stress responsive biomarkers are related to mental health outcomes. Data are from the TRAILS study, a large prospective population study of 715 Dutch adolescents (50.9 % girls), assessed at 16.3 and 19.1 years. Reactivity measures of the hypothalamic pituitary-adrenal (HPA) axis and autonomic nervous system (ANS) biomarkers (heart rate, HR; respiratory sinus arrhythmia, RSA; and pre-ejection period, PEP) to a social stress task were used to predict concurrent and longitudinal changes in internalizing and externalizing symptoms. Hierarchical linear modeling revealed relatively few single effects for each bio-marker with the exception that high HR reactivity predicted concurrent internalizing problems in boys. More interestingly, interactions were found between HPA-axis reactivity and sympathetic and parasympathetic reactivity. Boys with high HPA reactivity and low RSA reactivity had the largest in-creases in internalizing problems from 16 to 19 years. Youth with low HPA reactivity along with increased ANS activation characterized by both decreases in RSA and decreases in PEP had the most concurrent externalizing problems, consistent with broad theories of hypo-arousal. Youth with high HPA reactivity along with increases in RSA but decreases in PEP also had elevated concurrent externalizing problems, which increased over time, especially within boys. This profile illus-trates the utility of examining the parasympathetic and sym-pathetic components of the ANS which can act in opposition to one another to achieve, overall, stress responsivity. The framework of allostasis and allostatic load is supported in that examination of multiple biomarkers working together in con-cert was of value in understanding mental health problems concurrently and longitudinally. Findings argue against an additive panel of risk and instead illustrate the dynamic inter-play of stress physiology systems.

ABSTRACT: Replicating the group-based developmental trajectory method-ology from our prior study (Patriquin, Lorenzi, Scarpa, & Bell. 2014. Developmental Psychobiology, 56, 317-326), the current study examines the development of baseline respiratory sinus arrhythmia (RSA) across a new, larger cohort of typically developing children at 5, 10, 24, 36, and 48 months of age and examines the trajectory relationship with symptoms of childhood psychopa-thology. Group-based developmental trajectory modeling replicated our prior findings of a two-group model fit: a “High RSA ” and “Low RSA ” group. The “Low RSA ” group, which demonstrated lower baseline RSA across all time points, had significantly more childhood problems at 48 months, namely increased withdrawal, aggressive behavior, pervasive developmental problems, and oppositional defiant problems. All participants for whom there were developmental or autism spectrum concerns (n 6; based on maternal report at 48 months) were allocated to the Low RSA trajectory group. These results suggest that consistent developmental trajectories of RSA may point to protective factors (i.e., high RSA) against developing symptoms of childhood psychopathology.