Delirium is defined as a condition of disturbed consciousness, with reduced ability to focus, sustain, or shift attention.
The DSM V diagnostic criteria for delirium require:
A) A disturbance in attention (i.e., reduced ability to direct, focus, sustain, and shift attention) and awareness (reduced orientation to the environment).
B) The disturbance develops over a short period of time (usually hours to a few days), represents a change from baseline attention and awareness, and tends to fluctuate in severity during the course of a day.
C) An additional disturbance in cognition (e.g., memory deficit, disorientation, language, visuospatial ability, or perception).
D) The disturbances in Criteria A and C are not better explained by another preexisting, established, or evolving neurocognitive disorder, and do not occur in the context of a severely reduced level of arousal, such as coma.
E) There is evidence from the history, physical examination, or laboratory findings that the disturbance is a direct physiological consequence of another medical condition, substance intoxication, or withdrawal (i.e., due to drug abuse or a medication), or exposure to a toxin, or is due to multiple etiologies.
Delirium is often associated with a disturbance in the sleep-wake cycle. This disturbance can include daytime sleepiness, nighttime agitation, difficulty falling asleep, excessive sleepiness throughout the day, or wakefulness throughout the night. In some cases, complete reversal of the night-day sleep-wake cycle can occur. Sleep-wake cycle disturbances are very common in delirium and have been proposed as a core criterion for the diagnosis.
The individual with delirium may exhibit emotional disturbances, such as anxiety,
fear, depression, irritability, anger, euphoria, and apathy. There may be rapid and unpredictable shifts from one emotional state to another. The disturbed emotional state may also be evident in calling out, screaming, cursing, muttering, moaning, or making other sounds. These behaviors are especially prevalent at night and under conditions in which stimulation and environmental cues are lacking.
Adapted from American Psychiatric Association. Diagnostic and Statistical Manual of Mental Disorders. 5th ed. Washington, DC. American Psychiatric Association. 2013. p. 596. Internet. Accessed on May 23, 2016.