Which acute mental status change is characterized by sudden onset and may begin with delusions?

• A. Dementia
• B. Alzheimer disease
• C. Depression
• D. Delirium

Answer: (D)

Delirium is an acute confusional state defined by a sudden onset with rapid changes in attention and cognition that can fluctuate over hours or days. It often includes disorganized thinking and perceptual disturbances, such as delusions or visual misperceptions, that can appear early in the course. Because it starts abruptly and varies in its intensity, delirium signals an underlying medical issue (infection, metabolic disturbance, medication effects, withdrawal, hypoxia, etc.) and requires urgent evaluation and management.

Dementia and Alzheimer disease, by contrast, develop gradually over months to years with a steady decline in memory and function, and they do not typically present with the abrupt, fluctuating attention seen in delirium. Depression can cause cognitive complaints, but its pattern is not the abrupt, fluctuating inattention and arousal characteristic of delirium.