Delirium is best described as?

• A. a quick change in mental states
• B. a gradual memory decline
• C. a mood instability
• D. a sleep disorder

Answer: (A)

Delirium is an acute, fluctuating disturbance in consciousness and attention that develops over a short period, usually hours to days. The key point is the rapid onset and the variability of mental state within a day, reflecting a sudden disruption in how a person remains oriented and focused. This acute change is typically caused by an underlying medical condition, medication effect, infection, metabolic problem, or substance use/withdrawal, and it’s often reversible once the underlying issue is treated.

The other descriptions do not capture this pattern. Gradual memory decline aligns more with dementia, which progresses slowly and lacks the rapid, fluctuating disturbances in attention and consciousness. Mood instability points to mood disorders, not a sudden disturbance of awareness. A sleep disorder involves sleep-wake regulation and may accompany delirium, but it isn’t the defining feature of delirium itself.