A 28-year-old male presents to the psychiatry outpatient clinic 3 weeks after a motor vehicle accident in which he was the driver. His car collided head-on with a truck, and he sustained minor injuries. He reports intrusive memories of the crash, avoidance of driving, hypervigilance while traveling as a passenger, and sleep disturbance. He denies substance use and has no prior psychiatric history. On examination, he appears anxious and startles easily at sudden noises. What is the most likely diagnosis?

Explanation

## Diagnosis: Acute Stress Disorder (ASD) ### Timeline and Symptom Cluster **Key Point:** The patient presents 3 weeks post-trauma with a constellation of intrusive memories, avoidance, hyperarousal, and sleep disturbance—all hallmark PTSD symptoms. However, the critical distinguishing feature is the **duration of symptoms: 3 weeks falls within the ASD window (3 days to 1 month post-trauma)**. ### Differential Features: ASD vs PTSD | Feature | Acute Stress Disorder | PTSD | |---------|----------------------|------| | **Onset** | Within 3 days of trauma | Can be delayed; symptoms persist >1 month | | **Duration** | 3 days to 1 month | >1 month (by definition) | | **Symptom clusters** | Re-experiencing, avoidance, hyperarousal, dissociation | Re-experiencing, avoidance, negative mood/cognition, hyperarousal | | **Dissociation** | Often prominent (numbing, detachment, derealization) | Less emphasis in diagnostic criteria | | **Prognosis** | ~50% progress to PTSD; ~50% remit | Chronic if untreated | **High-Yield:** ASD is the **acute phase** diagnosis; PTSD is the **chronic phase** diagnosis. The 1-month threshold is the dividing line. ### Clinical Pearls **Clinical Pearl:** This patient meets full criteria for ASD: - **Trauma exposure:** Motor vehicle accident (criterion A met) - **Intrusive symptoms:** Flashbacks of the crash (criterion B) - **Avoidance:** Avoiding driving (criterion C) - **Negative mood/arousal:** Hypervigilance, sleep disturbance, exaggerated startle (criterion D) - **Duration:** 3 weeks (within ASD window) **Key Point:** Early intervention (cognitive-behavioral therapy, psychoeducation, sleep hygiene) in ASD may reduce progression to PTSD. [cite:DSM-5 Trauma and Stressor-Related Disorders]