Clinical Vignette
Patient: "Mr. A," 42-year-old firefighter, presenting 10 days after witnessing his partner crushed by a collapsing wall during a warehouse fire.
Chief Concern: "I can't stop seeing the wall come down on him. I hear the cracking sound even when there's nothing. I feel like I'm back in that fire whenever I close my eyes. During the incident, I went on autopilot — it felt like I was watching myself from outside my body."
History of Present Illness: Ten days ago, Mr. A witnessed his firefighting partner crushed by a collapsing wall during a warehouse fire. He attempted to free his partner from debris but was unable to; his partner died at the scene. During the event, Mr. A experienced peritraumatic dissociation: he describes leaving his body, watching from above, and the scene becoming silent despite ongoing noise. Since the event (10 days), he reports: vivid intrusive images of the wall collapse (10-15x daily), nightmares of the event (nightly), flashbacks when hearing cracking sounds, emotional numbness (cannot feel sad about his partner's death despite wanting to), avoidance of the fire station, hypervigilance (checking structural integrity of every building he enters), exaggerated startle to sounds, insomnia, irritability, and difficulty concentrating. He has been unable to return to work. He continues to experience episodes of depersonalization (feeling detached from his body) 2-3 times daily.
Past Psychiatric History: No prior psychiatric history. 15 years of firefighting with no previous critical incident stress reaction.
Family History: No psychiatric history.
Mental Status Exam: Alert but tense. Scans room upon entry. Speech slightly rapid. Mood 'numb.' Affect constricted, hypervigilant. During description of the event, became dissociated briefly (fixed gaze, delayed responses for ~15 seconds). No psychotic symptoms. Denies suicidal ideation. Insight good.
Step 1: Why ASD and Not Yet PTSD
The critical distinction: duration. ASD applies from 3 days to 1 month after trauma. PTSD applies only after 1 month. Mr. A is at day 10.
Criterion A: Exposure to actual or threatened death.
Witnessed partner's death from structural collapse. Direct exposure. MET.
Criterion B: ≥9 symptoms from any of 5 categories (intrusion, negative mood, dissociation, avoidance, arousal).
Intrusion: intrusive memories, nightmares, flashbacks (3). Negative mood: emotional numbing (1). Dissociation: peritraumatic + ongoing depersonalization (2). Avoidance: fire station, discussion of event (2). Arousal: hypervigilance, startle, insomnia, irritability, concentration difficulty (5). Total: 13 symptoms. ≥9 required. MET (13 symptoms).
Criterion C: Duration 3 days to 1 month.
Day 10 post-trauma. Within the ASD window. MET — ASD WINDOW.
Criterion D: Significant distress or impairment.
Unable to work. Sleep disruption. Functional impairment. MET.
Step 2: ASD vs. PTSD Timeline
| Feature | Acute Stress Disorder | PTSD | This Patient |
|---|---|---|---|
| Onset window | 3 days to 1 month post-trauma | >1 month post-trauma | ASD: day 10 |
| Symptom structure | 9+ from any category (flexible) | Cluster-specific thresholds required (B, C, D, E) | ASD criteria used |
| Dissociation emphasis | Prominent in diagnostic criteria | Captured via subtype specifier | Prominent peritraumatic and ongoing dissociation |
| Clinical trajectory | Many resolve spontaneously; some convert to PTSD | Diagnosis at >1 month reflects persistence | Monitoring needed at day 30 |
| Early intervention | Brief CBT (4-5 sessions) can prevent PTSD conversion | Full trauma-focused therapy | Early intervention indicated NOW |
Clinical Trajectory
Mr. A meets full ASD criteria at day 10. The severity of his presentation (13 symptoms, prominent dissociation, functional impairment) places him at elevated risk for conversion to PTSD. Brief trauma-focused CBT initiated now (within the ASD window) is the most effective intervention for preventing PTSD development.
Diagnostic Formulation
Diagnostic Conclusion
Acute Stress Disorder (F43.0): All DSM-5-TR criteria met at day 10 post-trauma. 13 symptoms across all 5 categories. Prominent dissociative features (peritraumatic and ongoing). High risk for PTSD conversion given symptom severity and dissociation prominence. Treatment: brief trauma-focused CBT (4-5 sessions starting immediately), psychoeducation about normal trauma responses, supportive workplace accommodation. Reassess at 30 days: if symptoms persist, diagnosis converts to PTSD.
Teaching Points
- The 1-month boundary between ASD and PTSD is the primary temporal distinction. ASD captures the acute response (3 days to 1 month). If symptoms persist beyond 1 month, the diagnosis changes to PTSD.
- ASD uses a more flexible symptom structure than PTSD: any 9 symptoms from 5 categories (without cluster-specific thresholds). This reflects the recognition that early trauma responses are more heterogeneous than established PTSD.
- Brief trauma-focused CBT during the ASD period (4-5 sessions) is the most effective early intervention for preventing PTSD. It has stronger evidence than psychological debriefing (single-session processing), which has NOT been shown to prevent PTSD and may worsen outcomes in some studies.
- Peritraumatic dissociation (dissociation DURING the traumatic event) is one of the strongest predictors of subsequent PTSD development. Mr. A's out-of-body experience during the fire is a significant risk factor.
- The 3-day minimum prevents diagnosing ASD for normal acute stress responses. Transient distress in the first 48 hours is expected after trauma and does not constitute a disorder. Only when symptoms persist beyond 3 days and cause significant impairment does ASD apply.