Investigating the interplay of physiological and psychological processes in fatigue in Long COVID

Thomas, Bethan ORCID: https://orcid.org/0009-0002-0294-6839 2025. Investigating the interplay of physiological and psychological processes in fatigue in Long COVID. PhD Thesis, Cardiff University. Item availability restricted.

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Abstract

Background Long COVID is a complex, chronic condition characterised by diverse symptoms, with fatigue among the most prevalent and debilitating. The mechanisms underlying this fatigue remain poorly understood. This thesis explores the interplay of psychological and physiological factors in long COVID fatigue, aiming to advance understanding and inform potential interventions. Methods This thesis comprises three studies. Study 1 is a scoping review examining how long COVID fatigue is defined and measured. Study 2 is a cross-sectional survey applying the Common Sense Model of Self-Regulation (CSM-SR) and active inference framework to examine interactions between fatigue and physiological (autonomic symptoms, interoception) and psychological (illness perceptions, distress) factors. Study 3 experimentally tests a sensory attenuation model of fatigue investigating mechanisms underlying long COVID fatigue. Results Findings reveal that long COVID fatigue remains inadequately defined and limited by measurement approaches. Across two empirical studies with 183 long COVID participants, fatigue was consistently severe and impactful, affecting both cognitive and physical domains. Results support the relevance of the CSM-SR, linking fatigue to cognitive illness perceptions and depression, and highlight the active inference framework, showing associations with interoception and autonomic symptoms. Findings highlight the utility of models integrating physiological, cognitive, and emotional processes. No evidence supported the sensory attenuation model of fatigue, suggesting this mechanism may not be central to long COVID. Conclusion Together, these studies provide a biopsychological account of long COVID fatigue. They highlight the need for clearer, more consistent definitions and measurement, revealing conceptual ambiguity that can limit progress in the field. They demonstrate that autonomic II symptoms, interoception, illness perceptions, and depression are associated with fatigue, offering new insights into the psychological-physiological interactions. By showing no evidence of altered somatosensory processing despite severe fatigue, the research redirects attention toward alternative mechanisms. Overall, this thesis provides a comprehensive examination of long COVID fatigue.

Item Type:	Thesis (PhD)
Date Type:	Completion
Status:	Unpublished
Schools:	Schools > Healthcare Sciences
Date of First Compliant Deposit:	14 April 2026
Last Modified:	14 Apr 2026 13:55
URI:	https://orca.cardiff.ac.uk/id/eprint/186304

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