Delirium

A disturbance in attention and awareness develops over a short period—usually hours to a few days—represents an acute change, and tends to fluctuate during the day.

Timing requirement

Onset window

Develops over hours to days; fluctuates

Timing in context

Evidence must support a direct physiological cause such as a medical condition, substance, withdrawal, toxin, or multiple etiologies.

Sources and review

Last content review: August 21, 2026