Understanding Long Covid: Why Functional Neurological Disorder Isn’t the Right Fit
Introduction to Long Covid
Long Covid, a term for prolonged symptoms following an acute Covid-19 infection, represents a diverse range of clinical symptoms and abnormal biological processes. Despite extensive research, a definitive cause for some of the most severe symptoms of long Covid—such as chronic fatigue, post-exertional malaise, cognitive impairments (often termed brain fog), and severe dizziness—remains elusive.
The Debate Around Functional Neurological Disorder
In light of these gaps in understanding, some medical professionals in the United States, United Kingdom, and beyond have suggested that Functional Neurological Disorder (FND) might explain many long Covid cases. However, this perspective is contentious. Prominent publications like The New Republic and Slate have endorsed this viewpoint, but applying the FND framework to long Covid is problematic. The support for FND is largely based on assumptions rather than robust evidence. Research into immunological, neurological, hormonal, and vascular abnormalities—already documented in long Covid patients—may offer more promising treatment avenues.
The Controversial History of FND
Functional Neurological Disorder evolved from the outdated Freudian concept of conversion disorder, where psychological trauma was believed to manifest as physical symptoms like paralysis. In the past, some individuals, especially women, were diagnosed with hysteria under similar frameworks. Recent updates in psychiatric diagnostic manuals have renamed and redefined these conditions. The 2013 DSM-5 update introduced the term “Functional Neurological Symptom Disorder,” aiming to provide a more neutral description. This change included new diagnostic criteria that required positive clinical signs inconsistent with recognized medical conditions.
Current Understanding and Treatment of FND
FND is currently described as a disorder related to disruptions in brain function, specifically the brain’s “predictive machinery” and sensory perceptions. Treatments typically involve psychotherapy and physical therapy targeting these supposed dysfunctions. Although some patients report improvements, many others face a poor prognosis.
Challenges in Diagnosing Long Covid
The Covid-19 pandemic has heightened awareness of symptoms that do not fit traditional diagnostic categories. Patients with long Covid often face challenges in getting appropriate diagnoses and treatments. While an FND diagnosis may offer some relief, others find it problematic and difficult to remove from their medical records.
The Role of Neuropsychiatric Features
Mood disorders like depression and anxiety, prevalent during the pandemic, can exacerbate symptoms. In long Covid, these features might be connected to underlying biological issues rather than being primary causes. The current conceptualization of FND does not adequately account for these complexities.
Scientific Findings and FND Limitations
Brain imaging studies show differences in brain activity and structures between individuals with and without FND diagnoses. However, these studies show associations rather than causative relationships, and their implications remain unclear. The 2013 rebranding of conversion disorder to FND aimed to address concerns about the validity of clinical signs, but the situation has not significantly improved.
The Need for Accurate Diagnoses
The expansion of FND diagnoses to include symptoms like dizziness and cognitive problems—common in long Covid—has sparked debate. While some researchers and clinicians argue that these symptoms may not fit the FND framework, others are investigating biological mechanisms behind these manifestations. Recent studies have linked cognitive symptoms in long Covid to biomarkers found in neurodegenerative diseases.
Conclusion: Moving Beyond FND
As long Covid continues to be a major cause of disability, it is crucial for medical professionals, researchers, and policymakers to rely on scientific evidence rather than speculative diagnoses. The focus should remain on understanding and managing the complex symptoms of long Covid through rigorous research and accurate diagnostics.
About the Authors
David Tuller, Dr.P.H., is a senior fellow in public health and journalism at the Center for Global Public Health at the University of California, Berkeley. His role is supported by donations from individuals with ME/CFS, long Covid, and related illnesses. Mady Hornig, M.D., is a psychiatrist and physician-scientist, and president of CORe Community, Inc. David Putrino, Ph.D., is the Nash Family Director of the Cohen Center for Recovery from Complex Chronic Illness and a professor at the Icahn School of Medicine at Mount Sinai.
