Delirium
A sudden change that needs attention
Delirium is a sudden change in attention, thinking and awareness. It develops over hours or days and often fluctuates. A new change needs medical assessment because delirium usually accompanies an acute illness, injury, medication effect, or a combination of causes.
If this is happening now
New sudden confusion needs medical assessment now. Contact the urgent or emergency medical service where the person is. If the person is hard to wake, has trouble breathing, shows signs of a stroke, has a seizure or head injury, or is getting worse quickly, call the local emergency number immediately (999 in the UK).
Delirium Support explains what to do and what to tell the clinical team. It gives general information, not advice about an individual.
What matters in practice
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The change is acute and often fluctuates
Delirium develops quickly. A person may be more confused at some times of day and clearer at others. This pattern differs from the usual slow development of most dementias, although delirium and dementia often occur together.
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Delirium can be quiet
Some people become agitated or distressed. Others become unusually sleepy, withdrawn, or less responsive. The quieter form is easy to miss.
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The cause or causes need attention
Assessment looks for the medical problems, medicines, pain, dehydration, surgery, or other factors contributing to the change. More than one factor may be present.
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Knowing the person's usual state helps
Relatives and carers can often say exactly what changed and when. That information helps clinicians judge whether the person's attention, alertness, or thinking differs from normal.
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Recovery can take time
Some people improve quickly when the causes are treated. For others, recovery is slower and uneven. Follow-up matters when thinking, function, sleep, or distress remain changed.
These points are consistent with NICE guideline CG103, SIGN guideline 157, and the review by Wilson and colleagues.
My work on delirium
My clinical and research work centres on the recognition, assessment and care of people with delirium. I led the original development of the 4AT in 2011 and remain responsible for its updates.
The 4AT gives clinicians a brief way to assess possible delirium and cognitive impairment. The first published validation study included 234 hospitalised older people. Its role, evidence, translations and practical guidance are kept together on the official 4AT website.
My wider work includes research, professional education, public information and scientific publishing. The links below lead to separate resources built for different needs. This page connects them; it does not try to replace them.
Find information
Choose the route that fits
Each site has one main audience and purpose.
Understand what is happening
Plain-English information about signs, urgent help, delirium and dementia, supporting someone, and recovery.
Visit Delirium Support CliniciansUse the 4AT
The assessment, scoring guidance, evidence, translations, frequently asked questions and case examples.
Visit the 4AT Clinicians and researchersCompare assessment tools
A referenced catalogue of delirium instruments, including their purpose, evidence, limitations and source access.
Visit Delirium Tools Students and health professionalsLearn about delirium
Structured online education about recognition, assessment and care.
Visit Delirium Academy Clinicians, researchers and policymakersRead analysis and commentary
Longer articles about delirium care, science, measurement and policy.
Visit Delirium Words Journalists and organisersRequest comment or a talk
Current roles, areas of expertise, approved biographies and the institutional contact route.
Media informationEvidence and guidance
- NICE CG103: DeliriumPrevention, diagnosis and management in hospital and long-term care.
- SIGN 157: Risk reduction and management of deliriumGuidance across home, care-home, hospital and hospice settings.
- Wilson JE and colleagues. Delirium. Nature Reviews Disease Primers. 2020.A detailed review of mechanisms, diagnosis, prevention, management and outcomes.
- Bellelli G and colleagues. Validation of the 4AT. Age and Ageing. 2014.The first published validation study of the 4AT, in 234 hospitalised older people.
Clinical information and links reviewed 22 July 2026.