Dementia and the Mental Capacity Act 2005

People with dementia may lose mental capacity and become unable to make some decisions. The Mental Capacity Act is the law in England and Wales that protects people who lack capacity to make a decision.

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What is the Mental Capacity Act?

As their condition progresses, people with dementia may become unable to make some decisions for themselves. When this happens, the person is said to lack the ‘mental capacity’ to make the specific decision at that time.

The Mental Capacity Act is the law in England and Wales that protects and supports people who lack capacity to make a decision. It also outlines who can and should make decisions for them.

The Mental Capacity Act covers important decision-making about a person’s property, financial affairs, and health and social care. It also covers everyday decision-making, such as decisions about what a person wears, what they eat and their personal care.

It does not cover decisions such as voting, making a will, marriage or divorce. For advice on these decisions, talk to a relevant professional or visit the government website (GOV.UK).

The Act can help people with dementia, their carers and professionals to make specific decisions and to plan for the future.

Mental capacity laws in Northern Ireland

Northern Ireland has different laws around mental capacity and offers different legal tools to manage loss of capacity. These include Enduring power of attorney and controllership.

Read more

What are the 5 principles of the Mental Capacity Act?

The Mental Capacity Act is based on five key principles or rules. These are:

  1. A person has the right to make decisions for themselves. You must assume that someone is able to make their own decisions, unless it is shown that they can’t do this. 
  2. A person should not be treated as being unable to make a decision unless they have been given all reasonable help and support to make and communicate their own decision.
  3. A person should not be treated as being unable to make a decision just because other people think they have made a bad decision.
  4. If a person lacks capacity, any decisions that other people make for them must be in the person’s best interests. (See the page 'Making decisions' for a best interests checklist.)
  5. If a person lacks capacity, the people making the decision for them must consider the option that is the least restrictive to the person’s rights and freedoms.

Does the person have mental capacity to make a decision?

When a person has ‘mental capacity’ it means they are able to make a specific decision at a specific time. People who can’t do this are said to ‘lack capacity’ to make the specific decision. This might be due to an injury. Or they might have a learning disability, a mental illness, or a condition that affects their brain – such as dementia.

To have mental capacity a person must be able to:

  • understand the information that is relevant to the decision they want to make
  • keep the information in their mind long enough to make the decision
  • weigh up the information that is available to make the decision
  • communicate their decision in any way – including talking, using sign language, or through simple muscle movements such as blinking their eyes or squeezing someone’s hand.

How might mental capacity be affected in a person with dementia?

When a person has dementia their mental capacity can change over time. It can also change in both the short term and the long term. For example, there might be days or even times of the day when the person can think more clearly. This means they may have capacity to make a decision at some times but lack capacity at other times.

A person may also have the capacity to make some decisions but not others. For example, a person may be able to decide that they want to go on holiday but not be able to make choices between transport or accommodation options. This is because some decisions involve having to take in more information, which may be harder for the person to process or understand.

Some decisions, such as whether to move into a care home, also involve many factors to weigh up and this may also be harder for the person to consider. Therefore, you should not assume that a person lacks the mental capacity to choose simpler decisions such as what they want to wear or eat just because they can’t make difficult financial or medical decisions.

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