Stress may augment somatic symptoms in central sensitivity syndromes (CSS) such as fibromyalgia, chronic fatigue syndrome, and irritable bowel syndrome. To test this hypothesis, we examined whether the association between COVID-19 stress and somatic symptom severity would be stronger in people with than without CSS and whether psychological flexibility would buffer the impact of this stress on symptom severity.
In a 2-sample, repeated cross-sectional design, we analysed questionnaire data from Dutch people with and without CSS, collected in two independent surveys: before the COVID-19 pandemic (2018; CSS: n = 194, non-CSS: n = 337) and at the peak of the pandemic (2020; CSS: n = 428, non-CSS: n = 1101). Somatic symptom severity, worry and stress due to the pandemic, and psychological flexibility were examined in regression analyses. Two stress operationalisations were analysed: stress levels during the peak of the pandemic, and a comparison of measurements in 2020 and 2018 (assuming higher stress levels in 2020).
Higher worry and stress during the pandemic (standardized β = 0.14), the presence of a CSS (β = 0.40), and lower psychological flexibility (β = -0.33) were all (p < .0001) associated with more severe somatic symptoms, but the associations of each stress operationalisation with somatic symptoms was not particularly strong in people with CSS (β = -0.026, p = .27; β = -0.037, p = .22), and psychological flexibility (β = -0.025, p = .18; β = 0.076, p = .35) did not buffer this association.
Findings do not support the hypotheses that COVID-19 stress augments somatic symptoms, particularly in CSS, or that psychological flexibility buffers this impact. Rather, COVID-19-related stress appears to have an uncertain impact on somatic symptoms.

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