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Acute stress reaction matters because ICD-11 (the 11th revision of the International Classification of Diseases) classifies it as a normal, expected reaction to overwhelming stress, not a mental disorder at all. It is described as a transient reaction to an exceptionally stressful event, with symptoms of anxiety, numbness, or dissociationA disconnection between a person's thoughts, feelings, memories, or sense of identity, often as a response to stress.Read more →, typically starting within minutes and resolving within days. For example, imagine a man involved in a serious road traffic accident who feels dazed, tearful, and detached from his surroundings for two days afterward, then returns to normal. In practice, that brief timescale and spontaneous recovery are exactly what defines this as a normal reaction rather than an illness.

Symptoms include anxiety, low mood, anger, despair, overactivity, or withdrawal, and can include dissociative features such as feeling detached from oneself, all emerging within minutes to hours of the stressor and usually settling within a few days. Because ICD-11 treats it as a normal variation of a stress response rather than a disorder, no formal diagnosis or specific psychiatric treatment is usually required, only support and reassurance. Picture emergency department staff reassuring the road traffic accident patient that his distress is an expected reaction, without starting any medication. In practice, this reassurance-focused approach is appropriate because acute stress reaction is expected to resolve on its own within days.

• A workplace offers a single debriefing session to every employee hours after a fatal accident. What does the evidence show about this?
• How does DSM-5 handle the picture that ICD-11 calls an acute stress reaction?
• Which factor most strongly predicts that someone will develop post-traumatic stress disorder after a traumatic event?

• PTSD (post-traumatic stress disorder), symptoms persisting beyond one month with flashbacks and avoidance, unlike acute stress reaction's resolution within days.
• Adjustment disorder, follows an identifiable stressor and can last up to six months, whereas acute stress reaction is shorter and follows an exceptionally severe stressor.
• Acute stress reaction, ICD-11 classifies it as a normal reaction, not a disorder, unlike PTSDPost-traumatic stress disorder, a condition triggered by experiencing or witnessing a traumatic event.Read more →, which is a formally diagnosable mental disorder.
• Major depressive episode, persistent low mood lasting at least two weeks, rather than the brief, mixed, self-resolving symptoms of acute stress reaction.

• Debriefing does not alter the duration of the acute reaction.
• It is specifically advised against rather than recommended.
• Trials have consistently failed to show a preventive effect.
• The two systems differ here, which is the point of the comparison.
• Dissociative symptoms may occur, but it is not classed as a dissociative disorder.

• Extract the defining phenomenology, duration, severity and functional-impact clues.
• Match the pattern to the most specific diagnostic or assessment construct.
• Actively test the closest look-alike against the missing or contradictory clue.
• Choose the precise term rather than a broader category that is merely compatible.