Okay, let's tackle this question. The patient is a 15-year-old girl who had a traumatic road traffic accident and has been experiencing symptoms since then. The key symptoms mentioned are fear of traveling on roads, nightmares, disturbed sleep, and reliving the accident repeatedly for three months.

First, I need to recall the diagnostic criteria for PTSD. PTSD is a mental health condition triggered by experiencing or witnessing a terrifying event. Symptoms include intrusive memories, avoidance of reminders, negative changes in thinking and mood, and changes in emotional responses. The duration of symptoms must be more than one month for a diagnosis. Since the girl's symptoms have persisted for three months, this fits.

The other options might include conditions like acute stress disorder, which has similar symptoms but lasts less than a month. Adjustment disorder could be a consideration, but it's usually in response to a stressor and doesn't involve the full range of PTSD symptoms. Phobias might also be considered, but they typically involve a specific fear without the re-experiencing of trauma.

The key here is the duration and the specific symptoms of re-experiencing the trauma, nightmares, and avoidance. These are hallmark signs of PTSD. The clinical pearl is to remember that PTSD requires symptoms lasting over a month, distinguishing it from acute stress disorder. So the correct answer should be PTSD.

**Core Concept**
Posttraumatic stress disorder (PTSD) is a psychiatric condition triggered by exposure to actual or threatened death, serious injury, or sexual violence. It is characterized by intrusive memories, avoidance, negative alterations in cognition/mood, and hyperarousal symptoms persisting for ≥1 month.

**Why the Correct Answer is Right**
This patient’s symptoms—recurrent re-experiencing of trauma (reliving the accident), nightmares, sleep disturbances, and avoidance of road travel—are classic features of PTSD. The duration (3 months) exceeds the 1-month threshold required for diagnosis. PTSD arises from neurobiological changes in the amygdala, hippocampus, and prefrontal cortex, altering fear processing and memory consolidation.

**Why Each Wrong Option is Incorrect**
**Option A:** Acute stress disorder (ASD) shares similar symptoms but occurs within 1 month of trauma and resolves within 1 month.
**Option B:** Adjustment disorder involves emotional/behavioral symptoms in response to stressors but lacks the full PTSD symptom cluster (e.g., re-experiencing, avoidance).
**Option C:** Specific phobia involves persistent fear of a specific object/situation but does not include trauma-related re-experiencing or nightmares.

**Clinical Pearl / High-Yield Fact**
Differentiate PTSD from ASD using **duration**: ASD lasts <1 month post-trauma, while PTSD requires symptoms for ≥1 month. Remember **“REMEMBER PTSD”** mnemonic: Re-experiencing, Avoidance, Negative alterations in cognition/mood, Hyperarousal. **Correct Answer: C. Posttraumatic stress disorder**

✓ Correct Answer: C. Post traumatic stress disorder