**Question:** A 30-year-old man is brought to the emergency department by the police, who arrested him for his unusual behavior. When questioned, he exhibits delusional symptoms, restless behavior, and an unusual sleep deprivation claim. Which of the following is the most likely preliminary diagnosis?

A. Psychosis due to substance abuse
B. Delirium due to sleep deprivation
C. Schizophrenia
D. Mania due to bipolar disorder

**Correct Answer:** B. Delirium due to sleep deprivation

**Core Concept:**
Delirium is a neurological condition characterized by acute onset of confusion, disorientation, and inattention, often caused by a variety of factors such as sleep deprivation, infections, medications, or dehydration. In this case, the most plausible cause is sleep deprivation, as the patient claims to have not slept for a week and believes that he is God.

**Why the Correct Answer is Right:**
The patient exhibits several clinical features that support the diagnosis of delirium due to sleep deprivation. He has been sleeping for a week and claims not to need sleep, displays rapid speech and agitation, and has a disheveled appearance. Furthermore, his behavior is extremely difficult to assess due to his agitation and disorientation, making it challenging to gather a comprehensive history.

**Why Other Options Are Incorrect:**
Option A (psychosis due to substance abuse) is less likely because there is no mention of a history of substance abuse or abnormal behavior after substance cessation. Option C (schizophrenia) and D (mania due to bipolar disorder) are less likely due to the acute onset and lack of a clear family or personal history of psychiatric disorders.

**Clinical Pearls:**
In a patient presenting with bizarre behavior and agitation, delirium due to sleep deprivation should be considered in the differential diagnosis, especially in the context of the patient's claim of not needing sleep. The patient's disorientation and agitation make it challenging to obtain a comprehensive history, which can be misleading in making a diagnosis. Always consider the possibility of delirium when dealing with patients presenting with acute confusion, agitation, and bizarre behavior, especially when sleep deprivation or other relevant factors are present.