The Common Phenotypes Hypothesis

The Common Phenotypes Hypothesis proposes that Functional Neurological Disorder (FND) may confuse common neurological presentations with a distinct disorder. Much like “dropsy” once described swelling caused by various underlying diseases, symptoms such as weakness, tremors, seizures and sensory disturbances may arise from different biological processes rather than a single disorder. The hypothesis questions whether the clinical signs used to diagnose FND identify a distinct condition or merely recognise symptom patterns shared across multiple diseases, potentially obscuring their underlying causes.

Posts

FND Study of Nearly 600,000 Patients Reveals Different Biological Patterns Behind Different Symptoms

2 days ago

FND Nope Moderator

A major 2026 study links FND diagnoses to inherited disorders, congenital abnormalities, neurodevelopmental conditions and early-life biological factors. But are these vulnerabilities to FND, or evidence that different biological diseases produce overlapping clinical phenotypes? We examine the findings through the Common Phenotypes Hypothesis.

The Diagnosis of the Gaps: FND and the Problem of Phenotype Overlap

3 weeks ago

Quackademic

Davenport et al.’s comparison of Long COVID, ME/CFS and FND has drawn criticism, but some apparent errors expose a deeper problem: when FND can resemble almost every common neurological phenotype, definitions can determine the answer before the differential even begins.

The FND Dualism Debate May Be Starting With the Wrong Question

1 month ago

FND Nope Moderator

A debate over whether FND is best understood through psychiatric, neurological or integrated explanations may be skipping a more fundamental question: what evidence establishes FND as a single underlying disorder rather than a recurring clinical phenotype?

When the Presentation Becomes the Disease

2 months ago

FND Nope Moderator

Dropsy was once treated as a disease until medicine discovered that it was merely a shared presentation of many underlying conditions. This article asks whether IBS and FND may represent similar umbrella categories that future medical advances will eventually divide into more precise diagnoses.

The Common Phenotypes Hypothesis

4 months ago

Christoff Spousal caregiver

An exploration of FND, positive rule-in signs, comorbidity, predictive processing, diagnostic closure, and whether functional symptoms may reflect common phenotypes arising from multiple underlying conditions.

FND Might Be Nothing More Than a CNS Reflex

1 year ago

Christoff Spousal caregiver

What do I mean when I hypothesize that Functional Neurological Disorder (FND) might be nothing more than a central nervous system reflex?