What is the distinguishing feature of delirium?

The distinguishing feature of delirium is acute confusion due to identifiable causes. Delirium is characterized by a rapid onset of confusion and disorientation that can fluctuate in severity over a short period of time. Underlying factors such as infections, metabolic imbalances, or substance withdrawal often contribute to its development. This acute change in mental status is typically temporary and can be resolved once the underlying cause is treated.

Long-term memory loss pertains more to chronic conditions like dementia rather than the acute nature of delirium. Permanent cognitive impairment would suggest a stable cognitive decline, which is not characteristic of delirium, as it tends to be a reversible condition. Additionally, delirium can indeed be related to medication or substance use, such as intoxication or withdrawal, which further differentiates it from conditions that are unrelated to these factors. The acute nature and identifiable causes make option B the correct answer.