Which of the following symptoms is characteristic of delirium?

Fluctuating consciousness is a hallmark symptom of delirium, distinguishing it from other cognitive disorders. In delirium, a person experiences variations in their awareness and responsiveness to the environment, which can shift throughout the day. This means that a patient may seem alert and oriented at one moment and then become confused or disoriented shortly after. This fluctuation can be influenced by various factors such as time of day, underlying medical conditions, medications, or substance use.

Stable personality changes, consistent memory loss, and progressive cognitive decline are more indicative of other psychiatric or neurocognitive disorders, such as personality disorders, dementia, or other forms of cognitive impairment, where symptoms do not typically fluctuate in the same manner as seen in delirium. Delirium is characterized by its acute onset and the rapid changes in cognitive function, primarily affecting attention and awareness, rather than showing stable or progressive patterns seen in long-term cognitive disturbances.