Part Two

ICD-10 Chapter V: Mental and Behavioural Disorders

(In ICD-11, this chapter is known as “Chapter 06”.)

ICD-10 Chapter V is also published as a specialty publication known as the “Blue Book” and is available as a PDF. This expands on the brief disorder descriptions in the Tabular List and includes diagnostic guidelines.

ICD-10 Classification of Mental and Behavioural Disorders Clinical descriptions and diagnostic guidelines: http://www.who.int/classifications/icd/en/bluebook.pdf

This is how “Fatigue syndrome” and “Neurasthenia” are classified in ICD-10 Chapter V:

Tabular List ICD-10 Version: 2019

Note the exclusion of Malaise and fatigueR53 ) and Postviral fatigue syndrome ( G93.3 ).

(Please refer to the “Blue Book” and to ICD-10 Online Version: 2019 for full categories, category descriptions, inclusions and exclusions.)


Chapter V

Mental and behavioural disorders


Neurotic, stress-related and somatoform disorders



F45  Somatoform disorders

F45.0  Somatization disorder

F45.1  Undifferentiated somatoform disorder

F45.8  Other somatoform disorders

F45.9  Somatoform disorder, unspecified

Psychosomatic disorder NOS

F48  Other neurotic disorders

F48.0  Neurasthenia  [Ed: Lengthy textual description of symptoms for neurasthenia omitted]

Fatigue syndrome  [Ed: Note: not “postviral”; not “chronic”]

Use additional code, if desired, to identify previous physical illness. 

Excludes:  asthenia NOS (R53)

burn-out (Z73.0)

malaise and fatigue (R53)

postviral fatigue syndrome (G93.3)

psychasthenia (F48.8)

Correspondence between DSM-IV and ICD-10

There was a degree of correspondence between the DSM-IV Somatoform Disorders categories and the equivalent disorder section in ICD-10: Chapter V. This table sets out how the two classification systems corresponded for Somatoform Disorders [1].

(The now retired) DSM-IV Codes and Categories for Somatoform Disorders and the ICD-10 Equivalents:

[1] Source: Mayou R, Kirmayer LJ, Simon G, Kroenke K, Sharpe M: Somatoform disorders: time for a new approach in DSM-V. Am J Psychiat. 2005;162:847–855. [Neurasthenia (classified in ICD-10: Chapter V at F48.0) is not categorized in DSM-IV.] 

ICD-10 Chapter XVIII

(In ICD-11, this chapter will be known as “Chapter 21”.)

Note the following classifications under R53 Malaise and fatigue. See “Notes” regarding R53.82 and US ICD-10-CM.

Note exclusion of Fatigue syndrome (F48.0) and Postviral fatigue syndrome (G93.3).


Chapter XVIII

Symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified


General symptoms and signs



R53 Malaise and fatigue

Asthenia NOS



· chronic

· nervous

General physical deterioration



Excludes:  debility:

· congenital (P96.9)

· senile (R54)

exhaustion and fatigue (due to)(in):

· combat (F43.0)

· excessive exertion (T73.3)

· exposure (T73.2)

· heat (T67.-)

· neurasthenia (F48.0)

· pregnancy (O26.8 )

· senile asthenia (R54)

fatigue syndrome (F48.0)

· postviral (G93.3)



For the most recent information on classification and coding of Postviral fatigue syndrome; Myalgic encephalomyelitis; and Chronic fatigue syndrome in ICD-10 and ICD-11 see my November 2020 report:

Update on classification and coding of PVFS, ME and CFS for ICD-11, v7 | November 2020

Content in ICD-11 will be populated for parameters, in accordance with the ICD-11 Content Model Style Guide. There is the potential for considerably more content to be included for diseases, disorders and syndromes in ICD-11 than appears in ICD-10, including Descriptions.

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