Why do personalities change?

One of the most distressing things about dementia is the way that it can change someone’s personality.

Personality is the combination of thoughts, feelings and behaviour that determines how a person acts in different situations. One of the most distressing things about dementia is the way that it can change someone’s personality.

At first, changes in personality may be due to changes in the way a person is feeling. Over time, symptoms like memory loss can mean that a person with dementia becomes more confused and disoriented. When they can’t make sense of the world or get something wrong, they may feel frustrated and angry with themselves.

Eventually, the illnesses that cause dementia may damage the parts of a person’s brain that control behaviour and personality. With some illnesses, this can happen quite early. They may not be able to control their emotions as well as they used to. They may become angry or upset with other people very easily. You might find it difficult to understand their feelings and they might not be able to tell you why they feel that way.


If someone seems angry with you, or lashes out at you, it can feel horrible. Remember that it’s not your fault, and it’s not their fault. A person with dementia loses the ability to put themselves in other people’s shoes. They may not realise they are upsetting you.

Sometimes, a person who is living with dementia becomes depressed. This means that they can feel sad and down, and have difficulty enjoying the things they used to. Depression is an illness that can happen to anyone, and it can be treated. A person who has dementia may be offered medicines or other treatments for depression.

The most important thing to remember is that a person with dementia still has feelings. They may feel angry, sad, scared or anxious, but they can also feel happy, safe or calm.

The people who help to support your relative will try to recognise what triggers feelings of anger or distress. They will do their best to help your relative feel as happy, safe and calm as possible.

This information was updated in November 2019 and is due for review in November 2021. Please contact us if you would like a version with references.