**Question:** Delusions are seen in all of the following, Except -

A. Schizophrenia
B. Bipolar Disorder
C. Major Depressive Disorder
D. Dementia

**Core Concept:** Delusions are false beliefs that are persistent, resistant to logical or factual argument, and unrelated to current life stresses. They are a prominent feature of several psychiatric disorders, particularly schizophrenia.

**Why the Correct Answer is Right:** Dementia is a general term for decline in cognitive function, usually due to brain disease or injury. While delusions can occur in dementia, they are not a core feature and are not as persistent or resistant to argument as in delusional disorders.

**Why Each Wrong Option is Incorrect:**

A. Schizophrenia: Delusions are a cardinal symptom in schizophrenia, occurring in approximately 80-90% of cases. Schizophrenia is characterized by positive symptoms, such as hallucinations and delusions, alongside negative symptoms and cognitive impairments.

B. Bipolar Disorder: Although delusions can occur in bipolar disorder, they are typically less common and less persistent than in schizophrenia. The primary symptoms of bipolar disorder involve mood swings and hypomanic or manic episodes.

C. Major Depressive Disorder: Delusions are less common and less persistent in major depressive disorder (MDD) compared to schizophrenia. MDD is characterized by persistent sadness, anhedonia, and other mood symptoms, with delusions being a less prominent feature.

**Clinical Pearl:**

Delusions are a key feature in schizophrenia, often reflecting a specific content (e.g., persecution, jealousy, reference, or grandiose delusions). In contrast, delusions in dementia or mood disorders are less persistent and less likely to reflect specific content themes. Understanding the differences between these disorders helps in making a proper diagnosis and tailoring treatment strategies.

**Correct Answer:** D. Dementia

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In summary, delusions are a prominent feature of schizophrenia, whereas they are less common, less persistent, and less likely to reflect specific content themes in dementia and mood disorders (bipolar disorder and major depressive disorder). This understanding helps in differentiating these conditions and making an accurate diagnosis for appropriate treatment.