**Question:** A 25 year old university student had a fight with the neighbouring boy. On the next day, while out, he started feeling that two men in police uniform were observing his movement. When he reached home in the evening he was frightened. He expressed that the police were after him and would arrest him. His symptoms represent -

A. Delusional disorder
B. Obsessive-compulsive disorder
C. Post-traumatic stress disorder (PTSD)
D. Depression

**Core Concept:**

The described symptoms involve perceptual disturbances, emotional distress, and disturbed cognition, which are consistent with a psychiatric disorder. In this scenario, we are examining the potential diagnosis based on the provided symptoms.

**Why the Correct Answer is Right:**

The correct answer is **C. Post-traumatic stress disorder (PTSD)** because the patient's symptoms align with the diagnostic criteria of PTSD. PTSD is a mental health condition that develops after experiencing or witnessing a traumatic event, such as a violent assault or a life-threatening situation. In this case, the traumatic event is the fight with the neighboring boy.

**Why Each Wrong Option is Incorrect:**

A. **Delusional disorder (A):** Delusional disorder involves persistent and irrational beliefs. The described symptoms focus on perceptual disturbances and emotional distress, not holding fixed, false beliefs.

B. **Obsessive-compulsive disorder (B):** Obsessive-compulsive disorder is characterized by persistent and intrusive thoughts (obsessions) and repetitive behaviors or mental acts (compulsions) that the individual feels driven to perform due to distress or anxiety. In this case, the patient is experiencing perceptual disturbances and emotional distress but not obsessions and compulsions.

D. **Depression (D):** Depression is a mood disorder characterized by persistent feelings of sadness, hopelessness, and loss of interest or pleasure in activities. While the patient is clearly distressed, the described symptoms primarily involve perceptual disturbances and do not align with the core features of depression.

**Clinical Pearl (Highlighted in Bold):** The clinical pearl is that traumatic experiences can lead to psychiatric symptoms such as those described in the question. In this case, the traumatic event (the fight) caused the patient to develop PTSD, leading to perceptual disturbances, emotional distress, and fear of being pursued by the police. PTSD is an appropriate diagnosis for this scenario as it is a well-established psychiatric disorder resulting from exposure to a traumatic event.