Category · F40-F48 block
F48 — Other neurotic disorders
Terminology note: F48 groups two named, unrelated presentations that do not fit elsewhere in F40-F45: neurasthenia, a persistent fatigue syndrome, and depersonalization-derealization syndrome, an unreality experience with preserved insight into its unreal nature.
What is this category?
F48.0 covers neurasthenia: persistent, distressing fatigue after minimal mental or physical exertion, not explained by a mood disorder or a medical condition. F48.1 covers depersonalization-derealization syndrome: a persistent or recurrent experience of feeling detached from one's own mental processes or body (depersonalization), or of one's surroundings feeling unreal (derealization), with insight preserved throughout — the person recognises the experience as a subjective change, not an objectively true alteration of reality.
Core diagnostic concept
Both F48 subtypes are defined partly by exclusion: neurasthenia requires that the fatigue is not better explained by a mood or anxiety disorder or a medical condition, and depersonalization-derealization syndrome requires preserved insight distinguishing it from a psychotic disorder, in which a person might genuinely believe their altered experience reflects objective reality.
Key diagnostic features
- Neurasthenia: fatigue after minimal exertion
- Persistent, distressing mental or physical fatigue following minimal exertion, with incomplete recovery through rest.
- Neurasthenia is not primarily a mood disorder
- Diagnosed only when the fatigue is not adequately explained by a depressive or anxiety disorder, or a medical condition.
- Depersonalization and derealization, with preserved insight
- The person recognises the unreality experience as a subjective, internal change, not an objectively true alteration — this preserved insight is the key distinguishing feature from psychosis.
- Distressing but not delusional
- The unreality experience is distressing precisely because the person knows it does not reflect actual reality.
How to weigh evidence
These learning labels are teaching aids, not official ICD-10 terminology (see Sources and Method).
- supports Persistent detachment from one's own body or surroundings, described as feeling unreal, with the person clearly stating they know this feeling does not reflect actual reality.
- consistent not decisive A person reports feeling 'tired all the time' without yet enough detail on whether a mood disorder or medical condition has been excluded.
- raises alternative The person appears to genuinely believe their surroundings or body have actually, objectively changed, rather than merely feeling that way subjectively.
- contradicts or weakens The fatigue or unreality experience is fully explained by an already-diagnosed depressive episode or medical condition.
- missing and necessary to ask Whether insight is preserved (the person knows the experience is subjective, not an objective change) and whether mood-disorder or medical explanations have been excluded.
Diagnostic boundary
F48.0 requires persistent post-exertional fatigue not better explained by a mood disorder or medical condition; F48.1 requires a persistent unreality experience with preserved insight, distinguishing it from a psychotic disorder.
Full comparisons:
Duration and course
Minimum duration: Not fixed by a single universal threshold for either subtype; persistence and exclusion of better explanations are more decisive than duration alone.
Course: Can be persistent or episodic for either subtype.
Included presentations
- Neurasthenia: persistent fatigue after minimal exertion, not explained by a mood disorder or medical condition.
- Depersonalization-derealization syndrome: persistent or recurrent detachment from one's own mental processes, body, or surroundings, with preserved insight into its subjective, unreal nature.
Exclusions and distinguishing presentations
| If this is true instead… | Consider | Why |
|---|---|---|
| Fatigue fully explained by an already-diagnosed depressive episode | F32 | Neurasthenia is diagnosed only when fatigue is not better explained by a mood disorder. |
| Loss of insight, with the person genuinely believing their body or surroundings have objectively changed | delusion equals schizophrenia | Preserved insight into the subjective, unreal nature of the experience is what distinguishes depersonalization-derealization syndrome from a psychotic disorder. |
Four-character subtypes (orientation)
A learner should check whether insight is preserved before applying F48.1 — a person who genuinely believes their surroundings have objectively changed, rather than merely feeling that way, is describing a psychotic symptom, not depersonalization-derealization syndrome.
- F48.0 — Neurasthenia
- Persistent fatigue after minimal exertion, not explained by mood disorder or medical condition. (in_depth)
- F48.1 — Depersonalization-derealization syndrome
- Persistent unreality experience with preserved insight. (in_depth)
- F48.8 — Other specified neurotic disorders
- A neurotic presentation not matching the named subtypes. (taught for orientation only, not separately assessed in this pilot)
- F48.9 — Neurotic disorder, unspecified
- A neurotic disorder identified but without enough information to specify further. (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 depersonalization-derealization syndrome from a psychotic experience
A 22-year-old describes recurrent episodes, over the past four months, of feeling as though she is watching herself from outside her body, and that her surroundings seem 'foggy and unreal, like a dream.' She finds this deeply distressing and says clearly, 'I know it isn't really happening, I know my surroundings are real, it just feels that way,' and has had normal medical and neurological investigation.
- Step 1 — Identify the core experience: detachment from her own body and a sense of unreality about her surroundings.
- Step 2 — Check insight: she explicitly states she knows this does not reflect objective reality — insight is fully preserved.
- Step 3 — Check for an organic cause: normal medical and neurological investigation.
- Conclusion — F48.1, Depersonalization-derealization syndrome — the preserved insight into the subjective, unreal nature of the experience distinguishes this clearly from a psychotic disorder.
Interactive practice
- Type A Exhausted by a short walk Recognition / application · Foundation
- Type B Watching herself from outside Boundary discrimination · Transfer
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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Explain what 'preserved insight' means for depersonalization-derealization syndrome and why it matters.
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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State the two conditions that must be excluded before diagnosing neurasthenia.
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 F48 groups two seemingly unrelated presentations together.
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
F48: F48 covers neurasthenia (persistent post-exertional fatigue, mood/medical causes excluded) and depersonalization-derealization syndrome (a persistent unreality experience with preserved insight).
Decisive boundary cues:
- Persistent fatigue after minimal exertion, not explained by mood disorder or medical condition -> weighs toward F48.0.
- A persistent unreality experience with the person clearly aware it is subjective -> weighs toward F48.1.
- Genuine belief that surroundings or body have objectively changed -> weighs toward a psychotic disorder instead.
Duration/course: No single fixed duration threshold for either subtype; persistence and exclusion of better explanations are more decisive.
Nearest alternatives: f32, f45
Common mistake: Treating a person's report of feeling detached or unreal as evidence of psychosis without first checking whether insight into its subjective nature is preserved.
Retrieval prompt: Does the person know this experience is subjective and not objectively true, or do they believe reality has actually changed?
(or use your browser's print function) Open full-page printable revision view →
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.