A 32-year-old woman presents to the psychiatry clinic 3 days after a motor vehicle collision in which her car was hit by a truck. She was hospitalized for 2 days with minor injuries. She reports intrusive images of the moment of impact, avoidance of driving, hypervigilance while walking near roads, and difficulty sleeping. She denies prior psychiatric history. On mental status examination, she is alert, oriented, and visibly anxious. What is the most likely diagnosis?

Explanation

## Diagnosis: Acute Stress Disorder (ASD) ### Timeline and Symptom Criteria **Key Point:** Acute stress disorder is diagnosed when PTSD-like symptoms occur within 3 days to 1 month following a traumatic event. In this case, symptoms began 3 days post-trauma, placing her squarely in the ASD window. **High-Yield:** The DSM-5 distinguishes ASD from PTSD primarily by onset and duration: - **ASD:** Symptoms present from 3 days to 1 month post-trauma - **PTSD:** Symptoms persist beyond 1 month (or onset may be delayed) ### Symptom Cluster Analysis This patient demonstrates: 1. **Intrusion symptoms:** Intrusive images of the collision 2. **Avoidance:** Avoiding driving (behavioral avoidance) 3. **Negative mood/cognition:** Sleep disturbance 4. **Arousal symptoms:** Hypervigilance **Clinical Pearl:** ASD requires a minimum of 9 symptoms across the five diagnostic clusters (intrusion, negative mood, dissociation, avoidance, arousal), and this patient meets criteria across multiple domains. ### Dissociative Features **Key Point:** ASD is distinguished from PTSD by the prominence of dissociative symptoms (depersonalization, derealization, numbing, reduced awareness, amnesia for trauma). While not explicitly stated here, dissociation is a hallmark of early post-trauma presentations and is part of the ASD diagnostic framework. ### Differential Considerations | Feature | ASD | PTSD | Adjustment Disorder | GAD | |---------|-----|------|---------------------|-----| | **Onset** | 3 days–1 month | >1 month (or delayed) | Within 3 months of stressor | Insidious; no clear trauma | | **Trauma required** | Yes, criterion A | Yes, criterion A | Identifiable stressor (not necessarily trauma) | No specific stressor | | **Duration** | 3 days–1 month | ≥1 month | ≤6 months (≤12 months if chronic) | ≥6 months | | **Dissociation prominent** | Yes | No (unless severe) | No | No | **Warning:** Do not confuse ASD with PTSD solely on symptom profile—the **timing is critical**. At 3 days post-trauma, PTSD cannot yet be diagnosed by definition. ### Why Not the Other Options? - **PTSD:** Requires symptoms to persist ≥1 month; at 3 days, the diagnosis is premature. - **Adjustment Disorder:** Typically involves a non-traumatic stressor and less severe symptomatology; does not capture the intrusive re-experiencing and hyperarousal typical of trauma responses. - **GAD:** Lacks a clear traumatic trigger and does not feature trauma-specific symptoms like intrusive imagery or avoidance of trauma-related cues.