Delirium is a sudden change in how a person thinks, pays attention and behaves. It develops over hours or days. It is a sign that the brain is under stress. The cause is usually a physical illness such as an infection, an injury or operation, or a change in medicines. Delirium is a medical emergency, so it needs prompt medical assessment.

There is often more than one cause. Common causes are infections, starting or stopping certain medicines, dehydration, constipation, pain and surgery. Older people are more likely to get delirium. So are people who are frail, or who have dementia, several long-term illnesses, or poor sight or hearing.

Delirium starts over hours or days. Dementia develops slowly, over months or years. Delirium often comes and goes during the day. A person who has dementia can also get delirium, and may then suddenly become more confused, agitated or withdrawn. A sudden change like this needs medical assessment.

Will they get back to normal?

Many people recover within days. For others, delirium lasts for weeks or months, and some people do not get back to how they were before. The book describes what recovery can be like and how families can help.

Delirium (Acute Confusion): A Family Guide

When someone you love suddenly becomes confused, you need clear answers

Delirium is a sudden change in thinking and attention, usually triggered by illness, surgery or medicines. It affects about one in four older people in hospital. Yet many families have never heard of it.

This book is for people who have had delirium, and for families and carers trying to understand a sudden change in someone they know. It explains what delirium is, what families might see, how clinical teams assess and treat its causes, ways relatives and carers can help, and what recovery can be like.

31 chapters in six sections
Advice for people living with dementia
Dr Sharmella Summan’s account of her own delirium
Illustrated with line drawings

The hardback edition of Delirium (Acute Confusion): A Family Guide, standing upright

The questions families ask

When delirium happens, families have urgent questions. The book answers these questions in plain English. It shows you how to help at the bedside, how to raise concerns with staff, and what to expect during recovery.

What is happening?

Delirium is a sudden change in how a person thinks, pays attention and behaves. It develops over hours or days. It is a sign that the brain is under stress. The cause is usually a physical illness such as an infection, an injury or operation, or a change in medicines. Delirium is a medical emergency, so it needs prompt medical assessment.

In the book: Chapter 1, Understanding delirium
Why did it happen?

There is often more than one cause. Common causes are infections, starting or stopping certain medicines, dehydration, constipation, pain and surgery. Older people are more likely to get delirium. So are people who are frail, or who have dementia, several long-term illnesses, or poor sight or hearing.

In the book: Chapter 3, What causes delirium?
Is this dementia?

Delirium starts over hours or days. Dementia develops slowly, over months or years. Delirium often comes and goes during the day. A person who has dementia can also get delirium, and may then suddenly become more confused, agitated or withdrawn. A sudden change like this needs medical assessment.

In the book: Chapters 24 to 26, Delirium and dementia
Will they get back to normal?

Many people recover within days. For others, delirium lasts for weeks or months, and some people do not get back to how they were before. The book describes what recovery can be like and how families can help.

In the book: Chapters 8, 13, 17 and 18

These answers come from the book and from the published research listed in the medical and editorial policy. Editorial responsibility: Professor Alasdair MacLullich. Page reviewed 25 September 2026.

The first page

The opening of Chapter 1, as it appears in the book.

Chapter 1Understanding delirium

Your mother, normally sharp, is struggling to follow the conversation, and is saying odd, puzzling things. Or your husband, recovering in hospital the day after a routine operation, is confused and anxious, and is insisting that the staff are not to be trusted and that he be taken home to safety.

This rapid and unsettling change is very often a condition called delirium.

Delirium is a sudden deterioration in a person’s mental functioning. This deterioration can take several forms including becoming obviously confused, being very sleepy and less responsive or being agitated, anxious, seeing things that are not real, or believing odd things.

A common phrase used to describe this is ‘They are not themselves.’

Delirium appears suddenly, within hours or days. This is very different from dementia, which arises slowly over months or years.

Continue reading Chapter 1

Why we wrote this book

Delirium is common, but the word itself is often not used.

Staff may say that a person is ‘confused’, or call it ‘post-operative confusion’ after surgery. The change may be put down to old age. Without the word delirium, it is hard for families to understand what is happening, to find information, or to ask the right questions.

We are doctors with many years of experience of looking after people with delirium. We wrote the book because many families, and many people who have had delirium, lack clear information and explanation. It draws on our work with patients, on many conversations with families, on recent research, and on patients’ own accounts of delirium.

Sharmella has also had delirium herself, as a patient in intensive care. She tells her own story in the book.

Words often used instead

confused
post-operative confusion
not themselves
old age

The word that leads to action

The word ‘confusion’ does not lead to specific actions. The word ‘delirium’ does.

From Chapter 1

In their words

My mum has had delirium many times, but no one ever called it that

Nicola Handley, family carer NIHR Dementia Policy Research Unit, Queen Mary University of London

We were worried he’d developed dementia and would never be the same.

A family caregiver HealthinAging.org, American Geriatrics Society

I wanted to understand what was happening to her and to know how I could help.

A family member SIGN delirium booklet for patients and carers

Quoted from published accounts. The people quoted have no connection with this book. Read more accounts from patients and families

Read Chapter 1 free

Chapter 1, Understanding delirium, explains what delirium is, how it differs from dementia and other conditions, what causes it and how families can help. The PDF has 18 pages, with the chapter’s four illustrations and the contents list for the whole book.

Prefer to read on screen first? Read the opening of Chapter 1 on this website.

The authors

Alasdair MacLullich

Professor of Geriatric Medicine, University of Edinburgh

Alasdair MacLullich is a hospital doctor and Professor of Geriatric Medicine at the University of Edinburgh. For more than 20 years, he has cared for people with delirium and researched the condition. He created the 4AT, a delirium test used in hospitals worldwide.

He works as a consultant physician at the Royal Infirmary of Edinburgh. He co-chaired the Scottish national guideline on delirium (SIGN 157, 2019), co-founded the European Delirium Association, and is Editor-in-Chief of its journal, Delirium.

Sharmella Summan

Doctor

Sharmella Summan has worked as a doctor in hospitals and general practice, and now works in a hospice. She has cared for many people with delirium and has experienced delirium herself as a patient. She tells her own story in this book.

The paperback of Delirium (Acute Confusion): A Family Guide beside a tablet showing the e-book cover

Publication details

Title: Delirium (Acute Confusion): A Family Guide to Sudden Changes in Thinking and Memory
Authors: Professor Alasdair MacLullich and Dr Sharmella Summan
Publisher: Delirium Support Press
Free now: Chapter 1 as a PDF, by email. Free information about delirium for families on Delirium Support.
Kindle e-book: Planned for the end of October 2026, from Amazon
Paperback and hardback: Planned for the same time, or soon after
ISBN: Paperback 978-1-918164-01-5
Hardback 978-1-918164-02-2

Page reviewed 25 September 2026. To hear when the book is published, sign up for Chapter 1 above.

Delirium (Acute Confusion): A Family Guide to Sudden Changes in Thinking and Memory