14th February 2025

Diagnosis of delirium

To meet DSM (Diagnostic and Statistical Manual of Mental Disorders)-5 criteria for a delirium diagnosis, the patient must show all 4 of the following:

• Attention deficit, e.g. poor concentration, distractible
• Cognitive deficit, e.g. memory, language, disorientation OR abnormal perceptions, e.g. hallucinations
• Acute timeline (i.e. hours or days) to develop, from their usual baseline
• Features suggesting a physiological cause, as discerned by history, examination and/or laboratory tests

The following additional features are also commonly present:

• Altered consciousness: drowsy or heightened arousal
• Altered physiological processes: altered sleep, appetite and mobility
• Behavioural change: agitation, aggression, altered communication, withdrawal
• Fluctuant nature: symptoms vary throughout the day

Delirium can be divided into clinical subtypes based on a comparison to the patient’s baseline:

• Hyperactive: increased arousal, agitation and aggression
• Hypoactive: lethargic, withdrawn, inactive or incoherent
• Mixed delirium includes features of both hyperactive and hypoactive delirium