Elsevier

Schizophrenia Research

Volume 184, June 2017, Pages 14-20
Schizophrenia Research

High psychosis liability is associated with altered autonomic balance during exposure to Virtual Reality social stressors

https://doi.org/10.1016/j.schres.2016.11.025Get rights and content

Abstract

Background

Social stressors are associated with an increased risk of psychosis. Stress sensitisation is thought to be an underlying mechanism and may be reflected in an altered autonomic stress response. Using an experimental Virtual Reality design, the autonomic stress response to social stressors was examined in participants with different liability to psychosis.

Method

Fifty-five patients with recent onset psychotic disorder, 20 patients at ultra-high risk for psychosis, 42 siblings of patients with psychosis and 53 controls were exposed to social stressors (crowdedness, ethnic minority status and hostility) in a Virtual Reality environment. Heart rate variability parameters and skin conductance levels were measured at baseline and during Virtual Reality experiments.

Results

High psychosis liability groups had significantly increased heart rate and decreased heart rate variability compared to low liability groups both at baseline and during Virtual Reality experiments. Both low frequency (LF) and high frequency (HF) power were reduced, while the LF/HF ratio was similar between groups. The number of virtual social stressors significantly affected heart rate, HF, LF/HF and skin conductance level. There was no interaction between psychosis liability and amount of virtual social stress.

Conclusion

High liability to psychosis is associated with decreased parasympathetic activity in virtual social environments, which reflects generally high levels of arousal, rather than increased autonomic reactivity to social stressors.

Introduction

Experiences of social stress are likely to be involved in the aetiology of psychotic disorders (van Os et al., 2010, van Os et al., 2008). Developmental trauma, densely populated urban environments and ethnic minority status are consistently associated with increased risk for psychotic disorders (van Os et al., 2010). Repeated exposure to social stress may lead to stress sensitisation, an increased response to social stressors in daily life, with cumulative effects resulting in lasting liability to emotional and psychotic reactivity (Collip et al., 2008). Stress sensitisation may involve neuroendocrine and physiological responses, including the autonomic stress response. The autonomic nervous system regulates unconscious bodily functions including heart rate, respiratory rate, sweat production and digestion. It is divided into the parasympathetic and the sympathetic branch, classically associated with “rest-and-digest” vs. “fight-and-flight” responses, respectively. Both parasympathetic and sympathetic activity is generally present and increase of activity in one branch is not necessarily accompanied by decreased activity in the other branch. Spectral analysis of heart rate variability can be used as a tool to study autonomic balance and relative contributions of each branch. The heart rate naturally fluctuates and variability in heart rate is considered a sign of cardiac adaptability. Rhythms of fluctuations occur at different frequencies. Parasympathetic input by the vagal nerve is related to respiration and mostly increases variance in the high frequency (HF) spectrum (Akselrod et al., 1981, European Society of Cardiology, A.H.A, 1996). On the other hand, oscillations at the low frequency (LF) band are determined by both sympathetic and parasympathetic activity and are correlated with baroreflex activity (European Society of Cardiology, A.H.A, 1996, Pagani et al., 1986, Pomeranz et al., 1985).

Previous research of cardiac autonomic control suggests the overall balance of the autonomic nerve system is disrupted in psychosis. Compared to healthy controls, patients with psychotic disorders had increased heart rate and decreased heart rate variability (Bär et al., 2005, Boettger et al., 2006, Chang et al., 2013, Clamor et al., 2014, Moon et al., 2013). Spectral analysis of heart rate variability consistently showed reduced power in the high frequency (HF) spectrum, thus pointing to decreased parasympathetic activity (Montaquila et al., 2015). Decreased parasympathetic input was correlated with more severe psychopathology (Chung et al., 2013, Toichi et al., 1999) and may result in an impaired capacity to recover from sympathetic activation in response to tasks or stressors (Akar et al., 2015, Castro et al., 2008, Montaquila et al., 2015).

It is yet unknown whether this aberrant autonomic response to stressors in psychosis patients generalizes to social stressors. One study investigated autonomic response to social stress using a video-recorded speech anticipation task, but this experiment did not trigger an autonomic response in psychosis patients or controls (Lincoln et al., 2015). To facilitate further understanding of autonomic stress response and the mechanism of stress sensitisation, there is a need for new experimental designs that allow control of intensity and type of ecological valid social stressors. Using Virtual Reality (VR), we designed an interactive 3-dimensional virtual world containing the social stress paradigms of high population density, ethnic minority status and hostile social environments, allowing the random allocation of individuals with different liability for psychosis to controlled experimental social risk environments (Veling et al., 2014). Exposure to virtual social stressors elicited paranoid thoughts and subjective distress in a dose-response manner (Veling et al., 2016). Participants with a high liability for psychosis reported more self-reported paranoia and subjective distress to virtual social environments.

The aim of this study was to examine the autonomic stress response in participants with different liability to psychosis before and during exposure to virtual social environments with varying levels of social stressors. We hypothesized, first, parasympathetic input is decreased in people with higher psychosis liability. Second, we expected increased sympathetic activation when the number of virtual social stressors is increased. Third, we expected an increased reactivity to increased social stressors in the high liability group related to a lack of parasympathetic compensation.

Section snippets

Participants

Individuals aged 18–35 with different phenotypic liability to psychosis were included: (1.) 55 patients with a first diagnosis of any psychotic disorder - except for substance-induced psychotic disorder and psychotic disorder due to a medical condition - established within the last five years, (2.) 20 patients at ultra-high risk (UHR) for psychosis, according to the Comprehensive Assessment of At-Risk Mental States (CAARMS) criteria (Yung et al., 2005), (3.) 42 unaffected siblings of patients

Sociodemographics

Heart rate variability data was available for 45 controls, 37 siblings, 17 individuals at ultra-high risk (UHR) for psychosis and 44 patients with a recent onset psychotic disorder. Sociodemographic characteristics of the study sample are displayed in Table 1. Patients with a psychotic disorder were more likely to be male and have lower education levels than controls. UHR patients were relatively younger and more likely to have smoked in the last 24 h than controls. Both UHR and psychosis

Main findings

High psychosis liability was associated with increased heart rate and decreased heart rate variability at rest and during exposure to virtual social environments. Both HF and LF power were decreased, whereas LF/HF ratio and skin conductance levels were unaltered compared to low liability groups. The differences indicate decreased parasympathetic activity and mostly unaltered sympathetic input in individuals with high psychosis liability. Increase of social stress in virtual social environments

Conflict of interest

The authors have no conflict of interest.

Contributors

Authors M.G. and W.V. designed the study. Authors J.C., R.P.-K. and O.H. conducted the study. Authors J.C. and A.R. conducted the data analysis. Author J.C. undertook the statistical analysis and wrote the first draft of the manuscript. All authors contributed to and have approved the final manuscript.

Acknowledgements

This work was supported by a Veni laureate to Dr. Veling from the Netherlands Organisation for Health Research and Development (916.12.013). The authors wish to thank Mathijs Deen, who assisted with the statistical analyses.

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