If you're navigating an FND diagnosis, you may hear it — or its close relatives — called several different things. This piece explains the terminology, its history, and why the name actually matters clinically.
The core terms
Functional neurological disorder (FND) is the current preferred name in modern clinical practice. It describes a syndrome of neurological symptoms — weakness, movement disorders, non-epileptic seizures, sensory changes, cognitive symptoms, dizziness — arising from altered nervous-system function rather than structural damage. The name is deliberately neutral about cause and emphasizes what the condition actually is (a disorder of function) rather than assumptions about mechanism.
Functional neurological symptom disorder is the full DSM-5 name for the same condition. Most clinicians shorten it to FND in daily practice.
Conversion disorder is the DSM-5 designation for a specific subset of functional neurological presentations — specifically those "with motor symptom or deficit" or "with special sensory symptoms." Under ICD-10 coding, you may see codes like F44.4 (conversion disorder with motor symptom) or F44.7 (functional neurological symptom disorder with mixed symptoms). Clinically and in modern usage, "conversion disorder" and "FND" refer to substantially overlapping conditions; the terms are often used interchangeably in the older literature.
Psychogenic movement disorder / psychogenic non-epileptic seizures (PNES) — older neurological usage. Still appears in some clinical writing but is being replaced by "functional movement disorder" and "functional (dissociative) seizures" or "functional non-epileptic seizures."
Hysteria — historical (18th–19th century) term. No longer used clinically.
Why the terminology changed
The move from "conversion" and "psychogenic" to "functional" reflects a fundamental shift in the model of what this condition is.
The older terms carried a specific implication: that symptoms are "converted" from unconscious psychological conflict into physical symptoms (conversion), or that they are "generated by the psyche" (psychogenic). Both terms encode a purely psychological causal model.
The modern understanding rejects the purely psychological causal model. FND is now understood as a biopsychosocial disorder — biological, psychological, and social factors converge to produce a real disorder of brain network function1. Neuroimaging shows altered network connectivity in FND, particularly in networks involved in self-agency and attention2. The condition is not caused by "hidden psychological trauma converting itself into physical symptoms" in the older Freudian sense.
That said, psychological factors — trauma histories, mood, anxiety, patterns of attention to symptoms — are still relevant. They're just not the sole cause. They're factors that interact with biological vulnerabilities and social contexts to produce the syndrome3.
Why the name matters clinically
The name affects care and outcomes:
Stigma. "Conversion" and especially "psychogenic" and "hysteria" carry significant stigma. Patients told they have "psychogenic seizures" often feel dismissed and don't engage in treatment. Patients told they have "functional non-epileptic seizures" or "FND" tend to engage more.
Clinical framing. The FND framing supports the modern positive-signs approach to diagnosis, the biopsychosocial treatment model, and the message that this is a specific, treatable condition. The conversion framing tends to support a diagnosis-of-exclusion approach and less-effective treatment.
Explanatory power. "FND" invites the neuroscience-based explanation ("your brain networks are miscommunicating, and here's how"), which is both more accurate and more therapeutically useful than "your unconscious mind is converting distress into symptoms."
Patient engagement. Patients who understand their condition as a specific, real neurological syndrome tend to engage more actively with rehabilitation than patients who understand their condition as a psychological failure to cope.
Practical implications
If you or a family member has been given a diagnosis of "conversion disorder" or "psychogenic non-epileptic seizures":
- These terms are not wrong. They are older names for what is now more commonly called FND (or functional dissociative seizures).
- If your care team is using older terminology but a modern treatment approach, that's often fine — some clinicians use "conversion disorder" for coding reasons while treating with modern protocols.
- If your care team is using older terminology and an older approach (diagnosis of exclusion, framing as "psychological," minimal active rehabilitation), it may be worth seeking a second opinion from a clinician who works with the modern FND framework.
The bottom line
FND, functional neurological disorder, functional neurological symptom disorder, and conversion disorder are closely related — largely overlapping — terms. "FND" is the current preferred term because it supports better care. The condition it describes is real, specific, and treatable regardless of which name is used.
For more on the modern understanding: Is FND Real? · FND: A Neuroscience-Informed Introduction · How Is FND Treated?.
If you'd like to talk about the mental-health-side of FND treatment, book a free 15-minute consultation.
References
1: Brigham and Women's Hospital. Functional Neurologic Disorder Standard of Care.
2: Physio-pedia. Functional Neurological Disorder.
3: Managing Functional Neurological Disorders — Australian treatment recommendations, 2024.