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Basic Neurosciences · Paper A

Hypochondriasis illness anxiety disorder

The idea

The point of this differential is not spotting health-related worry — plenty of conditions produce that. It is telling apart five different reasons a patient keeps returning to (or fleeing) the doctor. A fear of undiagnosed disease with few symptoms points to illness anxiety disorder, while a real distressing symptom with excessive focus on it points to somatic symptom disorder instead. A discrete attack of physical panic points to panic disorder, an unwanted thought neutralised by rituals points to obsessive-compulsive disorder, and a deliberate deception to occupy the sick role points to factitious disorder. Illness anxiety disorder itself is the one where the FEAR, not the symptom, does all the work — and it can look like constant checking or like total avoidance, which is exactly why the exam likes to disguise one as the other. In practice, the exam question is never simply whether fear is present; it is which specific fear, and expressed which way.

How it works

Illness anxiety disorder (the DSM-5 term for hypochondriasis): a persistent, disproportionate fear of having or developing a serious illness for at least six months, with absent or only mild physical symptoms and normal investigations; reassurance calms the fear only briefly. Presents as either the care-seeking type (frequent appointments, repeated tests) or the care-avoidant type (cancelled appointments, avoiding all medical contact) — opposite behaviours driven by the identical underlying fear.
Somatic symptom disorderone or more genuinely distressing physical symptoms plus excessive, disproportionate thoughts, anxiety or time devoted to those symptoms; may coexist with a real diagnosed illness. The weight sits on the SYMPTOM here, not on fear of an undiagnosed label.
Panic disorderrecurrent, unexpected panic attacks — discrete surges of fear peaking within minutes, with palpitations, breathlessness and a fear of dying — followed by at least a month of worry about further attacks; the fear is episodic, not a constant background belief.
Obsessive-compulsive disorder with health-related obsessions: recurrent, intrusive, unwanted thoughts about illness that the person recognises as excessive and tries to resist or neutralise with compulsions such as checking or reassurance rituals. The resisted, ego-dystonic quality of the thought is the key difference from illness anxiety disorder's sustained belief.
Factitious disorderdeliberate falsification, exaggeration or induction of signs and symptoms, with no obvious external reward, in order to assume the sick role — the patient consciously deceives rather than genuinely believing they are ill.
Malingeringdeliberate feigning driven by a clear external incentive (compensation, avoiding work, obtaining opioids) rather than an internal psychological need — for example, symptoms that resolve the moment a compensation claim concludes; not classed as a mental disorder in its own right.

How to spot it

A vignette describing multiple normal investigations, repeated reassurance-seeking, and a conviction that returns within days of each reassurance is describing illness anxiety disorder's care-seeking type.
A vignette describing cancelled appointments, active avoidance of health information, and a fear that contact with medicine will confirm a feared diagnosis is describing illness anxiety disorder's care-avoidant type.
A vignette describing a real, ongoing physical symptom (pain, fatigue) with excessive time and distress devoted to it, even alongside a genuine medical diagnosis, is describing somatic symptom disorder.
A vignette describing discrete, minutes-long episodes of physical panic symptoms with symptom-free gaps between them is describing panic disorder, not illness anxiety disorder.
A vignette describing an unwanted, intrusive health-related thought the person recognises as excessive, neutralised by a checking or washing ritual, is describing obsessive-compulsive disorder with health-related obsessions.
A vignette describing direct evidence of tampering, self-induced signs or fabricated results, with no clear external incentive, is describing factitious disorder.

Tell it apart

Weight of the pictureillness anxiety disorder = the FEAR is the whole complaint with few or no real symptoms; somatic symptom disorder = a real, distressing SYMPTOM is the whole complaint, with excessive worry layered on top.
Timingillness anxiety disorder's fear is a constant, low-grade background conviction; panic disorder's fear arrives as discrete, minutes-long attacks with clear symptom-free gaps between them.
Thought qualityillness anxiety disorder's belief is sustained and ego-syntonic (the person owns it); obsessive-compulsive disorder's health-related thought is intrusive, unwanted and resisted (ego-dystonic), neutralised by compulsions rather than lived with.
Honesty of the presentationillness anxiety disorder's fear is genuinely believed; factitious disorder involves conscious deception to occupy the sick role; malingering involves conscious deception for a clear external incentive such as compensation.
Conviction strengthillness anxiety disorder's fear is anxious but not delusional — it briefly responds to reassurance; delusional disorder, somatic type, is fixed and unshakeable, immune to any evidence at all.
Behavioural directionillness anxiety disorder can present as relentless care-seeking OR as complete care-avoidance — opposite behaviours from the identical underlying fear, which is why avoidance is easy to miss as a presentation of the same disorder.

Watch for

Assuming any patient who returns to the doctor repeatedly must have illness anxiety disorder — check whether a genuine, distressing physical symptom (somatic symptom disorder) is actually doing the work instead.
Missing the care-avoidant presentation because it looks like the opposite of health anxiety — cancelling every appointment and refusing to discuss symptoms is still illness anxiety disorder, just expressed as avoidance rather than checking.
Mistaking a panic attack's physical symptoms for evidence of a chronic disease-fear, when the episodic, minutes-long timing points to panic disorder instead.
Confusing an unwanted, resisted health-related thought neutralised by compulsions with a genuinely held belief — that pattern is obsessive-compulsive disorder, not illness anxiety disorder.
Assuming frequent medical presentation always means genuine belief — look for direct evidence of deception (tampered samples, self-induced signs), which marks factitious disorder instead.
Treating a fixed, unshakeable conviction the same as an anxious one — a belief that resists all evidence and cannot be talked down at all is delusional disorder, somatic type, not illness anxiety disorder.

Use it again

First askis the FEAR the whole complaint with few or no real symptoms, or is a real, distressing SYMPTOM the centre of the picture? The first points to illness anxiety disorder; the second to somatic symptom disorder.
If the fear arrives as discrete, minutes-long episodes with clear gaps between them, redirect to panic disorder rather than illness anxiety disorder.
If the health-related thought is unwanted, resisted and neutralised by a ritual rather than simply believed, redirect to obsessive-compulsive disorder with health-related obsessions.
If there is direct evidence of deception, ask whether an external incentive exists: none points to factitious disorder, a clear incentive (compensation, avoiding work) points to malingering instead.
If the belief is fixed and totally unshakeable, immune to every piece of counter-evidence, redirect to delusional disorder, somatic type rather than illness anxiety disorder.
Never assume care-avoidance rules out health anxiety — ask whether the same underlying fear could explain either checking or avoiding, since illness anxiety disorder covers both.

In detail

Hook — the patient who has seen every specialist and still isn't reassured

Picture a 38-year-old teacher who has had a normal (a heart tracing that checks the heart's electrical rhythm), two normal blood tests and a reassuring cardiologist's letter — and who is booking a fourth GP appointment tomorrow, convinced this time the doctors have missed a fatal heart condition. Every reassurance holds for about a day before the fear returns exactly as strong. This is not a patient inventing symptoms for attention, and it is not simple worry about health. This page is about the specific pattern that produces that loop: illness anxiety disorder, still widely known by its older name, hypochondriasis.

Plain definition

Illness anxiety disorder (the current diagnostic label; hypochondriasis is the older, still-common name for the same picture) is a persistent, disproportionate fear of having or developing a serious, undiagnosed illness, lasting at least six months, even though the person has few or no actual physical symptoms and repeated medical work-ups come back normal. The fear is genuinely believed — the person is not lying — but it sits well beyond what the evidence justifies, and normal test results only calm it for a short while before it creeps back.

The critical caveat — the symptoms are not the point

Here is the trap almost every exam candidate falls into: assuming any patient who keeps returning to the doctor with physical complaints has this condition. That is the wrong focus. In illness anxiety disorder the physical symptoms themselves are mild or absent — what drives the presentation is the fear of an undiagnosed disease. A patient with substantial, distressing physical symptoms (real pain, real fatigue) plus excessive worry about them has a different, related condition instead: somatic symptom disorder. Confusing the two is the single most commonly tested trap in this topic, and the fix is one question: is the weight on the symptom, or on the fear?

First principles — why the fear won't stay switched off

Start from a basic idea: everyone occasionally notices a bodily sensation and briefly wonders if it means something serious, then lets it go once reassured. In illness anxiety disorder, that "let it go" step fails. The person's attention keeps returning to bodily sensations, interprets ordinary ones (a normal heartbeat felt after exercise, a headache after a long day) as evidence of disease, and each reassurance — a normal test, a doctor's confident "you're fine" — produces only brief relief because the underlying fear was never really about that one test result. It was about the possibility of illness itself, which no single negative result can ever fully rule out. This is why the checking (repeated appointments, repeated self-examination, hours spent researching symptoms online) never actually resolves anything: it treats the wrong target.

Structured walk-through — two faces of the same fear

DSM-5 splits illness anxiety disorder into two presentations that look opposite but share the same core fear. The care-seeking type does what you would expect: frequent GP visits, repeated requests for tests, doctor-shopping when reassurance runs out. The care-avoidant type does the opposite — cancelling appointments, avoiding hospitals, refusing to discuss symptoms — because contact with medicine itself feels like the moment the feared diagnosis will be confirmed. A candidate who only learns the care-seeking picture will misdiagnose the avoidant patient as simply "not anxious about health," when avoidance IS the anxiety, just expressed the other way round.

Worked example: imagine two patients with an identical underlying fear of undiagnosed bowel cancer. Patient A calls her GP weekly, has had three colonoscopies in two years, and researches symptoms every night. Patient B has cancelled his last four routine check-ups and changes the subject whenever his family mentions his weight loss. Both have illness anxiety disorder; only their behavioural response to the same fear differs, and you can test yourself on this split before moving on: which of the two would a candidate wrongly clear as "not anxious"?

Look-alikes & differentials

Looks like illness anxiety disorder	How to tell it apart
Somatic symptom disorder	Real, distressing physical symptoms are the centre of the picture, not just the fear of a label
Panic disorder	Fear comes in discrete, minutes-long attacks with physical surges, not as a constant background belief
Obsessive-compulsive disorder with health-related	The health thought is unwanted and resisted, with to neutralise it, not a sustained belief
	The patient consciously deceives to occupy the sick role, rather than genuinely believing they are unwell
disorder, somatic type	The belief is fixed and unshakeable, immune to any evidence, not merely anxious and briefly responsive to reassurance

Diagnosis — how it is actually established

There is no blood test or scan for illness anxiety disorder — the diagnosis rests on the clinical history matching DSM-5's criteria: preoccupation with having or acquiring a serious illness for at least six months, minimal or absent somatic symptoms, a high level of health-related anxiety, and either excessive health-related behaviours (repeated checking) or maladaptive avoidance. Just as important as confirming these criteria is actively excluding a real physical illness first — the diagnosis is only safe once a reasonable medical work-up has genuinely ruled out organic disease, not simply assumed away.

Management — what is actually done, and whose guidance it follows

There is no single NICE guideline dedicated to illness anxiety disorder specifically, but UK practice draws on the same evidence-based approach recommended for related anxiety presentations: cognitive behavioural therapy (CBT, a talking therapy that identifies and reworks the thoughts and behaviours driving the fear) is first-line, focusing on reducing checking and reassurance-seeking behaviours and building of uncertainty rather than chasing more tests. An (a type of antidepressant medication that also treats anxiety) is a reasonable pharmacological option when anxiety is severe or CBT access is limited. Crucially, repeated reassurance and repeated investigation are not treatment — each new normal result briefly soothes the fear and then, in practice, reinforces the checking cycle that keeps the disorder going.

Exam pearl

The vignette will describe a patient with normal or minimal findings across multiple work-ups who remains convinced something serious has been missed, and the tempting wrong answer will usually be somatic symptom disorder or generalised anxiety disorder. The tell is what is actually described: are physical symptoms the substance of the complaint, or is fear of an undiagnosed disease the whole complaint with the symptoms almost incidental? Before you move on, see if you can explain to a friend why a patient who avoids every doctor's appointment can still have the very same diagnosis as one who never stops booking them.

In one line

Illness anxiety disorder is a persistent, disproportionate fear of serious undiagnosed illness with few or no real symptoms, expressed either as relentless care-seeking or as complete care avoidance — and reassurance never lasts, because it was never really about the test result.