Behaviour changes

Common behaviour changes that may occur when a person has dementia, why do these changes occur?

Answers to this and some general guidelines for coping with them.

Changes in the behaviour of a person with dementia are very common. This may place enormous stress on families and carers. It can be particularly upsetting when someone previously gentle and loving behaves in a strange or aggressive way.

Why does behaviour change?

There are many reasons why a person’s behaviour may be changing. Dementia is a result of changes that take place in the brain and affects the person’s memory, mood and behaviour. Sometimes the behaviour may be related to these changes taking place in the brain. In other instances, there may be changes occurring in the person’s environment, their health or medication that trigger the behaviour. Perhaps an activity, such as taking a bath, is too difficult or the person may not be feeling physically well. Dementia affects people in different ways. Understanding why someone is behaving in a particular way may help you with some ideas about how to cope.

Where to begin

Always discuss concerns about behaviour changes with a doctor, who will be able to check whether there is a physical illness or discomfort present and provide some advice. A doctor will be able to advise if there is an underlying psychiatric illness.


Coping with changed behaviours can be very difficult, and is often a matter of trial and error. Always remember that the behaviour is not deliberate. Anger and aggression are often directed against family members and carers because they are closest. The behaviour is out of the person’s control and they may be quite frightened by it. They need reassurance, even though it may not appear that way.

What to try

  • A calm, unstressed environment in which the person with dementia follows a familiar routine can help to avoid some difficult behaviours
  • Try to keep the environment familiar. People with dementia can become upset if they find themselves in a strange situation or among a group of unfamiliar people where they feel confused and unable to cope
  • The frustration caused by being unable to meet other people’s expectations may be enough to trigger a change in behaviour
  • If behaviour becomes difficult, it is best not to attempt any form of physical contact such as restraining, leading them away or approaching from behind. It may be better to leave them alone until they have recovered, or call a friend or neighbour for support
  • Try not to take it personally
  • Try not to use a raised voice
  • Avoid punishment. The person may not remember the event and is therefore not able to learn from it
  • Speak slowly, in a calm and reassuring voice
  • Try not to become provoked or drawn into an argument  


This can be physical, such as hitting out, or verbal such as using abusive language. Aggressive behaviour is usually an expression of anger, fear or frustration.

What to try

  • The aggression may be due to frustration. Locking the door may prevent wandering, but may result in increased frustration
  • Activity and exercise may help prevent some outbursts
  • Approaching the person slowly and in full view may help. Explain what is going to happen in short, clear statements such as “I’m going to help you take your coat off”. This may avoid the feeling of being attacked and becoming aggressive as a self-defense response
  • Check whether the aggressive behaviour is about getting what the person wants. If so, trying to anticipate needs may help.

Catastrophic reactions

Some people with dementia over-react to a trivial setback or a minor criticism. This might involve them screaming, shouting, making unreasonable accusations, becoming very agitated or stubborn, or crying or laughing uncontrollably and inappropriately. This tendency to over-react is part of the disease and is called a catastrophic reaction. Sometimes a catastrophic reaction is the first indication of the dementia. It may be a passing phase, disappearing as the condition progresses, or it may go on for some time.

Catastrophic behaviour may be a result of:

  • Stress caused by excessive demands of a situation
  • Frustration caused by misinterpreted messages
  • Another underlying illness

This behaviour can appear very quickly and can make family and carers feel frightened. However, trying to figure out what triggers catastrophic behaviour can sometimes mean that it can be avoided. Keeping a diary may help to identify the circumstances under which they occur. If this isn’t possible, you can find ways of dealing with the behaviour quickly and effectively using some of the guidelines listed earlier.


People with dementia may often appear driven to search for something that they believe is missing, and to hoard things for safekeeping.

Hoarding behaviours may be caused by:

  • Isolation - When a person with dementia is left alone or feels neglected, they may focus completely on themselves. The need to hoard is a common response
  • Memories of the past - Events in the present can trigger memories of the past, such as living with brothers and sisters who took their things, or living through the depression or a war with a young family to feed
  • Loss - People with dementia continually lose parts of their lives. Losing friends, family, a meaningful role in life, an income, and a reliable memory can increase a person’s need to hoard
  • Fear -  A fear of being robbed is another common experience. The person may hide something precious, forget where it has been hidden, and then blame someone for stealing it

What to try

  • Learn the person’s usual hiding places and check there first for missing items
  • Provide a drawer full of odds and ends for the person to sort out as this can satisfy the need to be busy
  • Make sure the person can find their way about, as an inability to recognise the environment may be adding to the problem of hoarding

Repetitive behaviour

People with dementia may say or ask things over and over. They may also become very clinging and shadow you, even following you to the toilet. These behaviours can be very upsetting and irritating.

What to try

  • If an explanation doesn’t help, distraction sometimes works. A walk, food or favourite activity might help
  • It may help to acknowledge the feeling expressed. For example “What am I doing today?” may mean that the person is feeling lost and uncertain. A response to this feeling might help
  • Do not remind the person that they have already asked the question
  • Repetitive movements may be reduced by giving the person something else to do with their hands, such as a soft ball to squeeze or clothes to fold

Helpful videos

Based on Understanding and dealing with challenging behaviour, Alzheimer Scotland – Action on Dementia.

For more information ring the National Dementia Helpline on 1800 100 500.