Acute Stress Disorder

Acute Stress Disorder shares much of the same symptom picture as PTSD — intrusive memories, dissociation, avoidance, negative mood, and heightened arousal — but is specifically diagnosed within the first month following a traumatic event, with onset from three days after the trauma. If symptoms persist beyond one month, the diagnosis is revised to PTSD. Acute Stress Disorder is an important focus of early intervention, since it identifies people at heightened risk of going on to develop PTSD.

Acute Stress Disorder requires exposure to a qualifying traumatic event (the same threshold as PTSD) along with nine or more symptoms drawn from any combination of five categories — intrusion, negative mood, dissociation, avoidance, and arousal — occurring from three days to one month after the trauma, and causing significant distress or impairment. Unlike PTSD, symptoms do not need to be distributed across all categories, only reach a total of nine or more from the combined pool.

Acute Stress Disorder reflects the brain's acute response to overwhelming trauma. Risk factors overlap substantially with those for PTSD, but dissociation occurring during the traumatic event itself (peritraumatic dissociation) is a particularly strong and specific predictor of developing Acute Stress Disorder and, subsequently, PTSD.

• Severity and nature of the traumatic exposure
• Dissociation during the traumatic event itself
• Prior trauma history
• Pre-existing psychiatric conditions
• Lack of immediate social support after the event

Acute Stress Disorder reflects immediate activation of the brain's fear and stress circuitry (amygdala and HPA axis) in the direct aftermath of trauma. Dissociative symptoms — feeling detached, in a daze, or unable to recall aspects of the event — are thought to reflect an acute protective numbing response that can become problematic if it persists or intensifies rather than gradually resolving.

• Intrusive memories, flashbacks, or nightmares of the trauma
• Dissociative symptoms: altered sense of reality, feeling detached or in a daze, gaps in memory of the event
• Persistent negative mood
• Avoidance of trauma-related reminders
• Sleep disturbance, irritability, hypervigilance, exaggerated startle response, and difficulty concentrating

• Exposure to a qualifying traumatic event (same threshold as PTSD)
• Nine or more symptoms from the combined categories of intrusion, negative mood, dissociation, avoidance, and arousal
• Onset and duration from 3 days to 1 month after the trauma
• Causes significant distress or impairment
• Not attributable to a substance or another medical condition

Conditions a psychiatrist will consider and rule out before confirming this diagnosis:

PTSD

Diagnosed if the symptom pattern persists beyond one month.

Adjustment Disorder

Diagnosed when the stressor does not meet the trauma threshold, or the symptom pattern doesn't meet the full Acute Stress Disorder criteria.

Dissociative disorders

Considered if dissociative symptoms are the overwhelmingly predominant, persistent feature independent of the acute post-trauma timeframe.

Normal acute stress reaction

Expected distress after a traumatic event that does not reach the full diagnostic symptom threshold.

• Clinical interview conducted soon after the traumatic event
• Acute Stress Disorder Scale
• Specific screening for dissociative symptoms
• Assessment of immediate safety and social support needs

Trauma-focused CBT is the primary evidence-based early intervention and has the best evidence for reducing progression to PTSD. Psychological first aid — practical and social support in the immediate aftermath — is important, while formal single-session 'psychological debriefing' is not recommended, as some studies suggest it can worsen outcomes.

Minimal medication use in the acute phase

Short-term treatment of severe insomnia or anxiety may be considered, but early benzodiazepine use is generally avoided given evidence it may worsen longer-term outcomes.

SSRIs

May be started if symptoms are severe or persisting toward the PTSD threshold.

Trauma-focused CBT

The strongest evidence for reducing the risk of progression from acute stress disorder to PTSD.

Psychological First Aid

Practical, non-intrusive support focused on safety, connection, and stabilization in the immediate aftermath of trauma.

Avoiding formal single-session debriefing

Structured, mandatory debriefing sessions immediately after trauma are not recommended given evidence they may worsen outcomes for some individuals.

• Prioritize safety and basic needs first: sleep, nutrition, and physical safety
• Reconnect with social support rather than isolating
• Avoid using alcohol or substances to cope
• Gradually resume normal routine as tolerated
• Avoid pressure to 'process' the trauma in detail before feeling ready

Many people with Acute Stress Disorder recover without progressing to PTSD, particularly with appropriate early support and treatment. However, Acute Stress Disorder is a strong predictor of elevated risk for developing PTSD if symptoms do not resolve, making early trauma-focused intervention valuable.

• Psychological first aid rather than formal debriefing
• Ensuring practical and social support is available immediately after trauma
• Early identification and trauma-focused treatment for those with significant symptoms
• Avoiding social isolation in the aftermath of a traumatic event

Provide practical and emotional support without forcing a detailed recounting of the traumatic event before the person is ready. Help meet basic needs — safety, rest, food — and encourage professional support if symptoms are severe or not improving within the first few weeks. Be patient with dissociative, 'spaced out' presentations, which are a recognized part of the acute stress response rather than a sign of something being fundamentally wrong.

1. American Psychiatric Association. Diagnostic and Statistical Manual of Mental Disorders, 5th Edition, Text Revision (DSM-5-TR).
2. World Health Organization. International Classification of Diseases, 11th Revision (ICD-11).