Functional disorders

The class of conditions where a bodily or cognitive process fails without anything being structurally wrong with it — and, for this wiki, the clearest place where an inferential account of interoception does explanatory work that a signal-transmission account cannot.

The definition, and what it commits to

Bonaz et al.’s glossary: “a medical condition that impairs the normal function or functioning of a bodily or cognitive process, in the absence of a structural pathology or other detectible organic process causing the impairment. Emotional psychological factors are often implicated in the pathogenesis.” With an important rider the older “medically unexplained symptoms” framing tends to lose: functional symptoms “also commonly comorbid with organic disorder.” Functional is not a synonym for absent, and not the residue left when tests come back clean.

The span the review gives it is wide and crosses specialty lines entirely: within neurology, functional motor disorders, functional (dissociative) seizures and functional amnesia; elsewhere, irritable bowel syndrome, functional heartburn, noncardiac chest pain, urological chronic pelvic pain syndrome, diffuse chronic pain and fibromyalgia, and subtypes of breathlessness and dysautonomia.

The interoceptive reading

The reason these conditions belong in an interoception wiki rather than in a psychiatry one is that the inferential account of symptoms makes a positive prediction about them, rather than treating them as unexplained.

The mechanism the wiki already holds, from Van den Bergh et al. (2017) via Quadt et al.: interoceptive signals stay below awareness while they fall within the expected range, surface when they generate precise prediction error, and become symptoms when the highest-posterior-probability hypothesis encodes an aberrant, disease-related cause. On that account a symptom is a perceptual inference, and an inference can be wrong in the absence of any peripheral abnormality — which is exactly the functional-disorder profile. schema-guided-symptom-perception is the same idea reached from panic research a decade earlier: patients reporting a racing heart that is not racing are reading a prior, not a pulse.

Bonaz et al.’s neurological findings fit this:

• In functional motor disorders, motor symptoms are accompanied by abnormal selective allocation of attention to the body, and interoceptive-sensitivity abnormalities correlate with patients’ propensity to focus on external bodily features (Ricciardi et al. 2016).
• In functional seizures, interoceptive deficits across dimensions predict dissociative symptoms and seizure frequency (Koreki et al. 2020) — a dose-response relation between interoceptive abnormality and symptom burden, which is stronger evidence than most of the review carries.

The review’s proposal is that “an interoceptive perspective may provide valuable insight for understanding and intervention in these difficult-to-manage conditions.” That is a hope, not a result; no intervention trial is cited.

Why the category is contested territory

Two cautions the wiki should keep attached.

First, the label has a history. “Functional,” “psychogenic” and “medically unexplained” have all been used to mean not really ill, and patients with these diagnoses are among the most poorly served in medicine. The inferential account is a genuine improvement precisely because it makes the symptom real — a false inference produces real experience and real disability — but the vocabulary it inherits does not automatically carry that improvement.

Second, the diagnostic boundary moves. IBS was a “functional gastrointestinal disorder” and is now, per Rome, a “disorder of brain-gut interaction”; the reclassification is itself an argument that these are mechanistic conditions rather than diagnoses of exclusion. What counts as “no detectable organic process” is a claim about current detection methods.

Where it touches the debates

Functional disorders are the sharpest case for is-more-interoceptive-awareness-better in its awkward direction. The pattern reported across them — elevated sensibility (symptom focus, self-reported bodily attention) alongside impaired or unrelated accuracy — is the discrepancy profile, not a deficit. Whatever the treatment implication is, it is not “notice the body more.” See interoceptive-taxonomy, interoceptive-trait-prediction-error, and interoceptive-training-clinical, where the deficit-to-treatment inference is worked through case by case.