Category · F40-F48 block
F40 — Phobic anxiety disorders
Terminology note: A phobia is an excessive, persistent fear of a specific object, activity, or situation that is out of proportion to any actual danger, leads to avoidance or is endured only with marked distress, and causes real functional impairment. Ordinary caution or mild discomfort around a situation many people find unpleasant is not, by itself, a phobic disorder.
What is this category?
F40 groups anxiety disorders in which fear is reliably triggered by a specific, identifiable external situation or object that does not currently present real danger. The three main subtypes are organised by what triggers the fear: agoraphobia (open or crowded spaces, travelling, or situations from which escape might be difficult), social phobia (scrutiny or evaluation by other people), and specific phobia (a single circumscribed trigger, such as an animal, height, or medical procedure).
Core diagnostic concept
The defining feature of F40 is that the anxiety is situationally bound — it occurs reliably in the presence of (or anticipation of) a specific trigger, and is reduced or absent when the trigger is avoided. This is what separates F40 from F41's free-floating anxiety, which is not tied to a specific external trigger in the same way.
Key diagnostic features
- Situationally bound fear
- Anxiety is reliably triggered by a specific object or situation, not present in a free-floating way across unrelated contexts.
- Disproportionate to actual danger
- The fear is excessive relative to any genuine risk the situation or object poses.
- Avoidance or endurance with marked distress
- The person either avoids the trigger, often restricting their life significantly to do so, or endures it with significant anxiety.
- Functional impairment
- The fear and avoidance pattern causes real difficulty in daily functioning, not merely subjective discomfort.
How to weigh evidence
These learning labels are teaching aids, not official ICD-10 terminology (see Sources and Method).
- supports A reliable, disproportionate fear reaction to a specific situation, with avoidance restricting daily activities.
- consistent not decisive A person says they 'don't love' a certain situation but attends it regularly without significant distress or avoidance.
- raises alternative Anxiety that occurs unpredictably, without any specific external trigger, across many different situations.
- contradicts or weakens The person engages with the supposed trigger regularly without significant distress or functional impact.
- missing and necessary to ask Whether the fear is genuinely disproportionate and functionally impairing, or a manageable, common discomfort.
Diagnostic boundary
F40 requires a fear that is situationally bound to a specific trigger, disproportionate to actual danger, and causes avoidance or marked distress with real functional impairment — not simply ordinary discomfort with a commonly disliked situation.
Full comparisons:
Duration and course
Minimum duration: Not fixed by a single threshold; clinical significance rests on the combination of disproportion, avoidance, and functional impairment rather than duration alone.
Course: Often persistent once established unless treated; severity is judged by how much avoidance restricts the person's life.
Included presentations
- Agoraphobia: fear of open or crowded spaces, travelling away from home, or situations from which escape might be difficult or help unavailable.
- Social phobia: fear of scrutiny or negative evaluation by other people in social or performance situations.
- Specific (isolated) phobia: fear restricted to a single circumscribed trigger, such as a particular animal, height, or medical procedure.
Exclusions and distinguishing presentations
| If this is true instead… | Consider | Why |
|---|---|---|
| Free-floating anxiety not tied to a specific external trigger | F41 | F41's anxiety disorders are not reliably bound to a specific situation the way F40's phobias are. |
| Ordinary, non-impairing discomfort with a commonly disliked situation | any fear is a phobia | A disliked but manageable situation, engaged with regularly and without significant functional impact, does not meet F40's disproportion and impairment requirements. |
Four-character subtypes (orientation)
A learner should not assume any strong dislike of a situation is a phobia — the defining features are disproportion, avoidance or marked distress, and genuine functional impairment together, not intensity of dislike alone.
- F40.0 — Agoraphobia
- Fear of open or crowded spaces, travel, or situations from which escape might be difficult. (in_depth)
- F40.1 — Social phobias
- Fear of scrutiny or negative evaluation by others in social situations. (in_depth)
- F40.2 — Specific (isolated) phobias
- Fear restricted to a single circumscribed trigger. (in_depth)
- F40.8 — Other phobic anxiety disorders
- A phobic pattern not matching the named subtypes. (taught for orientation only, not separately assessed in this pilot)
- F40.9 — Phobic anxiety disorder, unspecified
- A phobic anxiety disorder identified but without enough information to specify the trigger type. (taught for orientation only, not separately assessed in this pilot)
External causes to check first
Categories in this block require that the disturbance is not better explained by another external cause listed below. These short capsules are reminders, not full teaching modules.
External cause capsule — Organic, medical, or substance-related presentations resembling F40-F48
A reminder that a presentation resembling an anxiety, obsessive-compulsive, stress-related, dissociative, or somatoform disorder can instead be caused by a general medical condition (e.g. hyperthyroidism producing anxiety-like symptoms, a neurological condition producing genuine sensory or motor loss) or a substance/medication (e.g. caffeine or stimulant intoxication, sedative or alcohol withdrawal producing anxiety symptoms) rather than being a primary F40-F48 disorder, and that this should be actively considered before a primary F40-F48 classification is settled.
What to check:
- Timing: did the symptoms begin during or shortly after starting, stopping, intoxication with, or withdrawal from a substance or medication known to produce anxiety, dissociative, or somatic symptoms?
- Medical context: is there a known medical or neurological condition (e.g. thyroid disease, a cardiac arrhythmia, a neurological lesion) with a recognised association with the symptoms described?
- Adequacy of investigation: has an appropriate medical or neurological work-up actually been completed, rather than simply not yet undertaken?
- Course after the cause is addressed: symptoms that substantially improve once the medical condition is treated or the substance/medication is stopped weigh toward a secondary cause rather than a primary F40-F48 disorder.
A full teaching module on F00-F09 (organic mental disorders) or F10-F19 (substance-related disorders), or a general medical work-up, all of which are outside this capsule's scope.
Worked example — distinguishing a specific phobia from ordinary caution
A 29-year-old avoids all situations involving dogs, crossing streets and rearranging routes to avoid houses with dogs visible in the yard. He has held this pattern since a dog bit him as a child. He describes intense panic, sweating, and a racing heart even at the sight of a dog on a leash across the street, and has declined social invitations to friends' houses that have dogs, which has strained several friendships.
- Step 1 — Identify the trigger: dogs, a single circumscribed object.
- Step 2 — Check disproportion: intense panic reaction to a leashed dog at a distance is disproportionate to any actual danger.
- Step 3 — Check avoidance and functional impairment: rearranging routes and declining social invitations shows real avoidance with genuine impact on his life.
- Conclusion — F40.2, Specific (isolated) phobia — the fear is bound to a single trigger, disproportionate, and functionally impairing.
Interactive practice
- Type A Twelve years of avoiding the park Recognition / application · Foundation
- Type E Nervous about the toast, but doing it anyway Misconception correction · Foundation
Retrieval prompts
Try answering each of these from memory before revealing where to check. Nothing you think or type here is sent or saved anywhere.
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State the three features that distinguish a phobic disorder from ordinary situational discomfort.
Reveal answer location
Check Duration and course, Diagnostic boundary, or the rapid revision card below — the cue you need is one of those, in this category's own already-authored wording.
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Name the three main F40 subtypes and what triggers each is organised around.
Reveal answer location
Check Duration and course, Diagnostic boundary, or the rapid revision card below — the cue you need is one of those, in this category's own already-authored wording.
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Explain why free-floating anxiety without a specific trigger is not classified under F40.
Reveal answer location
Check Duration and course, Diagnostic boundary, or the rapid revision card below — the cue you need is one of those, in this category's own already-authored wording.
These self-checks are a personal study aid only, visible to you on this page for this visit — they are not stored and do not affect your mastery dimensions.
Rapid revision card
F40: F40 requires a disproportionate, situationally-bound fear that leads to avoidance or marked distress and causes real functional impairment.
Decisive boundary cues:
- A reliable, disproportionate reaction to a specific trigger with avoidance and functional impact -> weighs toward F40.
- Anxiety without a specific, identifiable trigger, occurring across many situations -> weighs toward F41 instead.
- Manageable discomfort without avoidance or functional impact -> not a phobic disorder at all.
Duration/course: No single fixed duration threshold; disproportion, avoidance, and functional impairment together are decisive.
Nearest alternatives: f41, f42
Common mistake: Treating any strong or intense fear as automatically phobic without checking disproportion, avoidance, and functional impairment.
Retrieval prompt: Is this fear disproportionate to actual danger, and does it cause real avoidance or functional impairment — or is it manageable discomfort with a disliked situation?
(or use your browser's print function) Open full-page printable revision view →
Related glossary terms
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Agoraphobia
Fear of open or crowded spaces, travelling away from home, or situations from which escape might be difficult or help unavailable if things go wrong. Classified under F40.0.
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Panic attack
A discrete episode of intense fear or discomfort that develops abruptly and peaks within minutes, accompanied by physical symptoms such as a racing heart, chest tightness, breathlessness, and a feeling of impending doom or loss of control. Recurrent, unexpected panic attacks with persistent worry about further attacks define panic disorder (F41.0).
Source basis
WHO ICD-10 international classification structure and code/title (ICD-10 Browser, 2019 English release).
Original educational synthesis, informed by general published clinical-education understanding of ICD-10 F40-F48; no verbatim CDDG or DCR text is reproduced. See Sources and Method for the full policy.
Last reviewed: 2026-09-16. Full policy: Sources and Method.
Educational resource only. This page and its cases teach ICD-10 classification reasoning using fictional scenarios. It does not diagnose real people and should not be used to assess yourself or anyone else. If you or someone you know is struggling with anxiety, intrusive thoughts, the effects of a stressful or traumatic event, or persistent physical symptoms, please seek prompt professional evaluation.