These complex relationships in symptom generation and persistence have been most extensively researched by those working in the field of functional disorders.
7 Specific linear causal processes within the organs and tissues are not able to explain all physical suffering. For some conditions, it is necessary to approach treatment holistically rather than on an individual pathophysiological basis. Effective treatments and rehabilitation approaches for functional disorders are known,
8 and many of them are already employed in long COVID clinics. However, explicit explanatory models that address the need for a multidisciplinary and integrated treatment provision are key to better clinical services. Poorly integrated explanatory models contribute to poor care and stigma for people who are ill in these specific ways.
In summary, we highly welcome research into the cellular and physiological mechanisms behind persistent symptoms, including post-viral fatigue. However, it is increasingly clear that simple, causative relationships between pathophysiology and symptoms inadequately explain many diseases and chronic health conditions, including long COVID. There is an available body of literature on the multiple factors involved in the generation, perception, and persistence of functional symptoms, and models through which to integrate these. We are moving into a new era in long COVID research and treatment that would benefit from an integrated paradigm through which to understand human illness. We suggest it is time to break taboos based on a dualistic understanding of physical versus mental illness and bring in existing knowledge about functional somatic symptoms to provide improved explanations and treatments.