F43.9 ICD-10-CA code: Reaction to severe stress, unspecified
F43.9 is the ICD-10-CA code for “Reaction to severe stress, unspecified” in CIHI’s FY 2026–2027 release, in effect from Apr 1, 2026.
Official description
F43.9Reaction to severe stress, unspecified
Short description: Reaction to severe stress unspecified
ICD-10-CA · Canada · Also written F439
Index terms
Entries in CIHI’s alphabetical index that lead to F43.9. Searching the index by the condition the note names is how coders reach this code.
- Stress, reaction
- Disorder (of), stress
- Reaction, stress (severe)
Notes for F43.9
As CIHI prints them, with any note F43.9 takes from the headings above it.
Includes
- Disorders of psychological developmentFrom Chapter 5: Mental and behavioural disorders (F00-F99)
Excludes
Conditions classified elsewhere.
- When associated with conduct disorder in F91.- (F92.8)From F40-F48 Neurotic, stress-related and somatoform disorders
- Symptoms, signs and abnormal clinical laboratory findings, not elsewhere classified (R00-R99)From Chapter 5: Mental and behavioural disorders (F00-F99)
Note
- This category differs from others in that it includes disorders identifiable on the basis of not only symptoms and course but also the existence of one or other of two causative influences: an exceptionally stressful life event producing an acute stress reaction, or a significant life change leading to continued unpleasant circumstances that result in an adjustment disorder. Although less severe psychosocial stress ("life events") may precipitate the onset or contribute to the presentation of a very wide range of disorders classified elsewhere in this chapter, its etiological importance is not always clear and in each case will be found to depend on individual, often idiosyncratic, vulnerability, i.e. the life events are neither necessary nor sufficient to explain the occurrence and form of the disorder. In contrast, the disorders brought together here are thought to arise always as a direct consequence of acute severe stress or continued trauma. The stressful events or the continuing unpleasant circumstances are the primary and overriding causal factor and the disorder would not have occurred without their impact. The disorders in this section can thus be regarded as maladaptive responses to severe or continued stress, in that they interfere with successful coping mechanisms and therefore lead to problems of social functioning.From F43 Reaction to severe stress, and adjustment disorders
Where F43.9 sits
- 1ChapterChapter 5: Mental and behavioural disorders (F00-F99)
- 2Block F40-F48Neurotic, stress-related and somatoform disorders
- 3Category F43Reaction to severe stress, and adjustment disorders
- 4Valid code F43.9Reaction to severe stress, unspecified
Source and release
- Data release
- ICD-10-CA · FY 2026–2027
- Effective date
- Apr 1, 2026
- Publisher
- CIHI
This page is built from the ICD-10-CA catalog that Vero Codes reads when it suggests codes: Canadian Institute for Health Information’s FY 2026–2027 release, imported from the publisher’s file and checked against it. The description, notes and structured data come from the same record.
Frequently asked questions
What does ICD-10-CA code F43.9 mean?
F43.9 is the ICD-10-CA code for “Reaction to severe stress, unspecified” in CIHI’s ICD-10-CA FY 2026–2027 release.
Where is F43.9 in ICD-10-CA?
F43.9 sits under F43 Reaction to severe stress, and adjustment disorders, within F40-F48 Neurotic, stress-related and somatoform disorders, within Chapter 5: Mental and behavioural disorders (F00-F99).
What coding notes apply to F43.9?
ICD-10-CA lists Note, Excludes, Includes notes for F43.9, including those from the headings it sits under. They are listed on this page with where each one comes from.
Which ICD-10-CA release does this page use?
It uses CIHI’s FY 2026–2027 release, in effect from Apr 1, 2026 to Mar 31, 2027. It is a reference: confirm the code against the current list and the payer’s rules before you submit it.