What is meant by ‘Mental Capacity’ and how is it assessed?

‘Mental Capacity’ is not a complicated concept and people other than doctors can assess it, though when there is doubt or argument, it is obviously wise to get an expert in. Basically, Mental Capacity means the ability to make decisions. In an MDMD context, it means the ability to make decisions about accepting or declining medical (and surgical) treatment and about Medically Assisted Rational Suicide (MARS) if that is being considered. Mental Capacity may also be important for decisions about making a will or managing finances. While they involve similar considerations, they are not relevant to this discussion except to make the point that Mental Capacity is context-specific. For example, a patient may not be able to understand a complex financial transaction but may be able to understand a simple yes-no treatment decision.

One reason why Mental Capacity assessments are usually not complicated is that the law – specifically, The Mental Capacity Act of 2005 – presumes that an individual has Mental Capacity unless there is evidence to the contrary on a balance of probability. That evidence will usually involve a medical diagnosis of mental illness (including dementia) or of a physical illness that affects brain function, such as a head injury, delirium caused by a high fever, a brain tumour, or a brain infection such as meningitis or encephalitis. However, such a diagnosis, even if unchallenged, does not by itself create a presumption that the patient lacks Mental Capacity. It must also be shown that the illness or condition has effects on basic abilities like awareness, memory and understanding that make decisions impossible or invalid. The Act also requires that patients be given appropriate help to make decisions, so that those with impaired vision, hearing or mobility are not unjustly excluded.

To quote from the advice given by one of the doctors’ professional insurance organisations:

“To be able to make a decision a person should be able to:
Understand the decision to be made and the information provided about the decision. The consequences of making a decision must be included in the information given.
Retain the information – a person should be able to retain the information given for long enough to make the decision. If information can only be retained for short periods of time, it should not automatically be assumed that the person lacks capacity. Notebooks, for example, could be used to record information which may help a person to retain it.
Use that information in making the decision – a person should be able to weigh up the pros and cons of making the decision.
Communicate their decision – if a person cannot communicate their decision – for example, if they are in a coma – the Act specifies that they should be treated as if they lack capacity. You should make all efforts to help the person communicate their decision before deciding they cannot.”

A patient’s decision is not invalid simply because a doctor disagrees with it, even when a serious psychiatric illness has been diagnosed. The classic case involved a long-term schizophrenic patient in Broadmoor – a secure hospital for what used to be called the criminally insane. His doctors thought that his leg needed to be amputated to save his life. The patient refused but was not over-ruled because he clearly understood the risk. In the event, he kept his leg – and survived. However, someone with a more acute mental illness – especially if it were severe enough to require compulsory admission – might be regarded as lacking capacity because his or her state of mind was too changeable or confused for proper assessment, or because it was likely to change with appropriate treatment – voluntary or otherwise. Such situations rarely arise in end-of-life contexts, especially where an Advance Decision makes the patient’s considered opinion very clear.

The main exception is when the mental illness is dementia that is so far advanced that the patient cannot retain any memory of previous discussions or is unable to have any sort of coherent discussion in the first place. That is why anybody who wants to plan for the possibility of MARS in Switzerland if they get Alzheimer’s or similar disorders should be aware that both the decision and the journey need to be made well before the dementia reaches a stage when Mental Capacity is lost, or likely to be lost. Alzheimer dementia usually progresses slowly and fairly steadily, thus allowing time for careful thought and planning. Arteriosclerotic dementia – caused by repeated small strokes – progresses less predictably and may worsen quite suddenly following a larger stroke, or a stroke affecting a part of the brain that is particularly important for decision-making or communication.

A case that was much discussed at the time involved a patient who was alleged by her psychiatrists to lack the Mental Capacity to refuse kidney dialysis, without which she would quickly die. She said repeatedly that she had had not merely a good life but rather a wild and selfish one and did not want to stay alive now that she had lost her looks, her health and the ability to attract the sort of rich husbands on whom she had successively relied for her extravagant and hedonistic lifestyle. Her psychiatrists said that her wish to die was due to a treatable and reversible condition, possibly caused by her underlying physical conditions. The judge disagreed and stated specifically that he preferred the opinion of an independent and experienced legal professional who had also interviewed her. The patient was allowed to die and entered history as the ‘Champagne Suicide’.

Dr Colin Brewer
Retired psychiatrist and MDMD Associate Coordinator