FND: New Name, Same Old Problems?

01 Oct 2026 0 comments

There is a great deal of talk about progress in Functional Neurological Disorder (FND). More specialist clinics, more conferences, more publications, greater professional recognition and increasingly sophisticated explanations of how the brain supposedly produces functional symptoms. But how much of this progress has actually changed what happens to patients?

Historically, we had hysteria, conversion disorder and psychogenic neurological disorders. Today, we have FND, accompanied by terminology involving brain networks, predictive processing and altered agency. The language has changed considerably, but the fundamental question remains: have we actually solved the diagnostic and therapeutic problems associated with these earlier concepts, or have we simply become better at describing them?

New Wine in Old Bottles

In their 2021 paper, A Historical Review of Functional Neurological Disorder and Comparison to Contemporary Models, Geoffrey Raynor and Gaston Baslet examine the evolution of FND through centuries of changing explanations. Their review identifies substantial continuity between historical and contemporary conceptualisations, despite changes in terminology, proposed mechanisms and clinical approaches.

The authors conclude with the French expression plus ça change, plus c'est la même chose: the more things change, the more they stay the same. This is particularly relevant because it comes from researchers examining the history of the diagnosis itself, rather than from critics simply rejecting it.

Modern FND is not identical to historical conversion disorder. Psychological trauma is no longer required for diagnosis, and greater emphasis is placed on positive clinical signs. But changing diagnostic criteria does not automatically demonstrate that the underlying reasoning is more reliable. A new explanation is not necessarily a demonstrated explanation, and a new diagnostic framework does not erase the failures associated with its predecessors.

Conditions previously mistaken for hysteria, conversion disorder or psychogenic movement disorders did not disappear when the terminology changed. Where similar assumptions and diagnostic methods survive, similar mistakes remain possible. The relevant question is which historical weaknesses have actually been overcome, and what evidence demonstrates that improvement.

When Changing the Name Becomes the Achievement

In his paper, Hysteria, Conversion and Functional Disorders: A Neurological Contribution to Classification Issues, neurologist Edward Reynolds questioned whether the proposed replacement terminology was sufficiently well founded. His concern extended beyond the offensiveness of historical labels to the conceptual clarity of their replacements.

The word functional has carried different meanings throughout medical history. Replacing an unpopular diagnosis with an ambiguous term does not necessarily produce a better-defined disorder. It may simply make the diagnosis more acceptable without resolving the underlying uncertainty.

A related criticism appears in Anton Scamvougeras and David Castle's 2024 paper, Functional Neurological Disorders: Challenging the Mainstream Agnostic Causative Position. The authors challenge the modern tendency to avoid committing to a psychological explanation while presenting FND through the language of altered neurological functioning.

They argue that efforts to reduce stigma have contributed to changes in how the diagnosis is framed, and question whether this represents genuine conceptual progress. Their preferred psychological explanation is itself open to criticism, but their challenge to the modern terminology raises an important question: has the underlying understanding changed, or has the presentation become more acceptable?

This is not merely a semantic argument. A patient who rejects a psychogenic explanation may be considerably more receptive to being told that their brain networks are functioning differently. But unless the proposed mechanism has been demonstrated in that patient, the newer explanation may communicate more certainty than the evidence warrants.

Progress in Recognition Is Not Progress in Understanding

Modern neuroimaging research has identified group-level differences in brain activity and connectivity among patients diagnosed with FND. However, these findings have not produced a validated biological test capable of establishing the diagnosis in an individual patient. Proposed mechanisms remain under investigation, and the relationship between observed brain activity and the actual cause of symptoms remains unresolved.

There is also a methodological problem when researchers compare patients diagnosed with FND against healthy controls. Differences between those groups do not necessarily establish that the findings are specific to FND. Without appropriate comparisons against patients with other neurological or psychiatric conditions, it can be difficult to determine what the findings actually distinguish.

Treatment evidence raises similar questions. The 2024 Physio4FMD randomised controlled trial, involving 355 participants, found that specialist physiotherapy was not significantly superior to usual neurological physiotherapy on its primary measure of physical functioning at 12 months. Some secondary outcomes favoured specialist treatment, including patients' perceptions of improvement, but the primary result remains important. Subjective improvement and demonstrably better physical functioning are not interchangeable outcomes.

None of this establishes that research has achieved nothing. It demonstrates why institutional growth, theoretical development and therapeutic breakthroughs must be distinguished. Counting publications or opening additional clinics does not establish that diagnostic accuracy has improved, that fewer patients are being misdiagnosed or that more people are achieving lasting recovery.

Making the Language More Acceptable

There is another uncomfortable possibility. What happens when we replace terminology patients find offensive with language they find reassuring, without adequately changing the underlying clinical reasoning? A patient may believe they are receiving a fundamentally different, scientifically established explanation when some of the older assumptions remain embedded in the assessment.

This is where supposedly compassionate language can become misleading. When uncertainty is concealed and hypotheses are presented as established facts, patients may reasonably experience this as gaslighting. Making a diagnosis easier to accept is not the same as making it more accurate, and reassuring terminology is not a substitute for an honest explanation of what remains unknown.

There is a useful parallel in South Africa, where cities and roads are renamed to reflect historical and cultural change. Such changes may carry symbolic importance, but renaming a road does not repair its potholes, create employment or lift its residents out of poverty. The name changes while the material problems remain. The same distinction applies to medicine: changing what we call something does not necessarily change what we know about it or what we can do for the people affected.

The Problems That Survive the Name Change

Perhaps the most important unresolved issue is falsifiability. When a patient diagnosed with FND deteriorates, develops additional neurological signs or fails to respond to treatment, what would cause the original diagnosis to be reconsidered? If every unexpected development can be accommodated through additional explanations, including comorbidity, symptom variability or treatment resistance, the diagnosis risks becoming increasingly difficult to challenge.

This is particularly relevant when considering historical misdiagnosis. Raynor and Baslet discuss Eliot Slater's 1965 criticism of hysteria diagnoses, including his concerns about the reliability of the diagnosis. They also discuss limitations of Slater's work and subsequent evidence suggesting lower misdiagnosis rates. Historical figures cannot simply be transferred to modern FND, but neither does a change in terminology demonstrate that the underlying diagnostic vulnerabilities have disappeared.

Indeed, the historical literature remains relevant precisely because it allows us to examine which assumptions, clinical practices and diagnostic limitations have survived successive changes in terminology. If a modern framework claims to have overcome the weaknesses of its predecessors, it should be possible to demonstrate how.

Consider the practical implications. If a patient diagnosed with conversion disorder in 1990 would receive an FND diagnosis today, would the investigations, diagnostic reasoning and eventual outcome be substantially different? In some cases, perhaps. In others, the same underlying assumptions may survive under a different name. The mere existence of a modern diagnostic framework cannot answer that question.

What Exactly Are We Celebrating?

Progress should ultimately be judged by what has become demonstrably more accurate, what has become better understood and what has measurably improved for patients. Institutional recognition can be valuable, but it cannot answer those questions on its own.

The historical review by Raynor and Baslet documents continuity between older and newer concepts. Reynolds questions whether the replacement terminology is sufficiently well founded. Scamvougeras and Castle challenge the conceptual foundations of the modern reframing. These authors do not necessarily agree about what FND is or how it should be understood, but their work provides reasons to question whether changes in language have been accompanied by equally substantial changes in knowledge.

If the terminology has changed, the institutions have expanded and the explanations have become more sophisticated, but the same diagnostic uncertainties and treatment limitations remain, then what exactly are we celebrating?

Patients need more than a diagnosis that sounds better. They need one that is demonstrably reliable, remains open to correction and leads to meaningful improvements in their lives. Otherwise, we risk mistaking the appearance of progress for progress itself.

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