**Question:** Delusions are seen in all the following except:

A. Schizophrenia
B. Bipolar disorder
C. Major depressive disorder
D. Substance-induced psychosis

**Core Concept:** Delusions are fixed, false beliefs that are not based on reality and persist despite substantial evidence to the contrary. They are a central feature of various psychiatric disorders.

**Why the Correct Answer is Right:** Delusions are not specific to a single disorder but are commonly seen in conditions like Schizophrenia, Bipolar disorder, and Substance-induced psychosis. On the other hand, Delusions are not typically present in Major depressive disorder, which primarily involves mood symptoms and cognitive impairments but not fixed, false beliefs.

**Why Each Wrong Option is Incorrect:**

A. Schizophrenia: Delusions are a key feature of schizophrenia, which is characterized by positive symptoms (delusions, hallucinations) and negative symptoms (flat affect, alogia, avolition).

B. Bipolar disorder: Delusions can occur during the depressive phase of bipolar disorder, but they are not a defining feature of the disorder. Instead, bipolar disorder is characterized by mood swings between mania and depression.

C. Major depressive disorder: As mentioned earlier, delusions are not a feature of Major depressive disorder, which primarily involves mood symptoms like depressed mood, anhedonia, and psychomotor retardation.

D. Substance-induced psychosis: Delusions may be present in substance-induced psychosis due to the effect of the substance on the brain, but they are not specific to this condition. Substance-induced psychosis refers to psychotic symptoms resulting from substance use or withdrawal.

**Clinical Pearl:** While delusions are not exclusive to a single disorder, understanding the specific symptoms and features of each disorder is crucial for arriving at an accurate diagnosis and appropriate treatment. A thorough clinical history, including substance use, is essential in differentiating between various psychiatric disorders and substance-induced psychosis.

**Correct Answer:** C. Major depressive disorder

**Core Concept:** Major depressive disorder is a mood disorder characterized by persistent sadness, anhedonia, and psychomotor retardation. Delusions are not a key feature of this disorder, which primarily focuses on emotional and behavioral symptoms.