Under the terms of the Mental Capacity Act (2005), all adults are presumed to have sufficient capacity (the ability to use and understand information to make a decision) to decide on their own medical treatment unless there is significant evidence to suggest otherwise.
The evidence has to show that:
- a person's mind or brain is impaired or disturbed, and
- the impairment or disturbance means that the person is unable to make a decision at the current time
Examples of impairments or disturbances in the mind or brain include:
- mental health conditions, such as schizophrenia (a condition that causes hallucinations and delusions) or bipolar disorder (manic depression – when your moods swing from one extreme to another)
- dementia (an ongoing decline of mental abilities, such as memory and understanding)
- serious learning disabilities
- long-term effects of brain damage
- physical or mental conditions that cause confusion, drowsiness or a loss of consciousness
- delirium (mental confusion)
- intoxication caused by drug or alcohol misuse
Someone is thought to be unable to make a decision if they are unable to:
- understand information about the decision
- remember that information
- use that information as part of their decision-making process, or
- communicate their decision by talking, using sign language or by any other means
If someone makes a decision about treatment that most people would consider to be irrational, it does not constitute a lack of capacity if the person making the decision understands the reality of their situation.
For example, a person who refuses to have a blood transfusion because it is against their religious beliefs would not be thought to lack capacity. This is because they understand the reality of their situation and the consequences of their actions.
However, someone with anorexia (an eating disorder) who is severely malnourished yet rejects treatment because they refuse to accept that there is anything wrong with them, would be considered incapable. This is because they do not understand the reality of their situation.
Changes in capacity
Your capacity to consent can change. For example, you may have the capacity to make some decisions but not others, or your capacity may come and go.
In some cases, people can be considered capable of deciding some aspects of their treatment but not others. For example, a person with severe learning difficulties may be capable of deciding on their day-to-day treatment, but incapable of understanding the complexities of their long-term treatment.
Some people with certain health conditions may have periods when they are capable and periods when they are incapable. For example, a person with schizophrenia may have periods when they are considered capable, but they may also have psychotic episodes (when they cannot distinguish between reality and fantasy) during which they are not considered capable.
Your capacity can also be temporarily affected by:
- shock
- panic
- fatigue (extreme tiredness)
- medication
If you know that your capacity may change, you can make an 'advance decision’ (previously known as an advance directive), stating how you would like to be treated in case of future incapacity (see the box to the right).
If a person specifically states in their advance decision that they do not want to undergo a particular treatment, this is legally binding. The only exception may be if that person is being held under the Mental Health Act (1983). This is an act that allows some people with mental health problems to be compulsorily detained in a psychiatric hospital.
The Directgov website has more information about mental health and the Mental Health Act (1983).
