1. There is clouding of consciousness, i.e., reduced clarity of awareness of the environment, with reduced ability to focus, sustain, or shift attention.
2. Disturbance of cognition is manifest by both:
   1. impairment of immediate recall and recent memory, with relatively intact remote memory;
   2. disorientation in time, place, or person.
3. At least one of the following psychomotor disturbances is present:
   1. rapid, unpredictable shifts from hypoactivity to hyperactivity;
   2. increased reaction time;
   3. increased or decreased flow of speech;
   4. enhanced startle reaction.
4. There is disturbance of sleep or of the sleep-wake cycle, manifest by at least one of the following:
   1. insomnia, which in severe cases may involve total sleep loss, with or without daytime drowsiness, or reversal of the sleep-wake cycle;
   2. nocturnal worsening of symptoms;
   3. disturbing dreams and nightmares, which may continue as hallucinations or illusions after awakening.
5. Symptoms have rapid onset and show fluctuations over the course of the day.
6. There is objective evidence from history, physical and neurological examination, or laboratory tests of an underlying cerebral or systemic disease (other than psychoactive substance-related) that can be presumed to be responsible for the clinical manifestations in Criteria A–D.

Comments
Emotional disturbances such as depression, anxiety or fear, irritability, euphoria, apathy, or wondering perplexity, disturbances of perception (illusions or hallucinations, often visual), and transient delusions are typical but are not specific indications for the diagnosis. A fourth character may be used to indicate whether or not the delirium is superimposed on dementia:
Delirium, not superimposed on dementia
Delirium, superimposed on dementia
Other delirium
Delirium, unspecified