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  • Writer's pictureChristie Roberts

Mental Capacity Assessments

Updated: May 27

People make thousands of decisions every day. Big and small, significant and insignificant- from choosing what to have for breakfast, to what to spend your money on, whether to start a new medication, undergo surgery, or to go out and get absolutely plastered. Typically, people have no problem making these decisions. However, in health and social care settings, there may be situations where someone is not able to make a decision for themself- known as 'lacking capacity'. Mental capacity cannot be applied to certain decisions- such as marriage, divorce, voting, and sexual relationships (CQC, 2011).

There's lots of information from SCIE (Social Care Institute for Excellence) and the CQC (Care Quality Commission- the regulatory body for health and social care in the UK), and I will be referencing these throughout, alongside my personal experiences of assessing capacity and having capacity assessed. As far as I'm aware, this information applies to England, Wales, Scotland and Northern Ireland- but please double check any additional information that may be applicable to the devolved nations. Internationally, different guidance, legislation and policy will exist.

The guiding principle for assessing capacity comes from the Mental Capacity Act (2005)(MCA). This gives a more comprehensive definition of lacking capacity: 'a person lacks capacity in relation to a matter if at the material time he is unable to make a decision for himself in relation to the matter because of an impairment of, or a disturbance in the functioning of, the mind or brain'. (Gov.UK, 2024).

This definition gives us a lot of additional information that relate to capacity assessments, which I'll discuss further. It's worth noting that the MCA exclusively uses male pronouns (he, himself etc), but does definitely apply to all gender identities. The first 2 points make up the initial '2 step test' for assessing capacity (SCIE, 2024).

1. Unable to make a decision for himself in relation to the matter

Assessing this is known as the functional test. The last part referring to 'the matter' links to capacity needing to be assessed for a specifc decision or matter at hand- we'll come back to this later. The decision that a person may lack capacity to make needs to be specified to understand whether or not a person is unable to make that decision. A capacity assessment should relate to a singular decision and not be extrapolated to other decisions- someone lacking capacity to accept medical treatment does not automatically mean they also lack capacity to choose what to wear, or vice versa.

2. Because of an impairment of, or a disturbance in the functioning of, the mind or brain

This is known as the diagnostic test. An impairment of the mind or brain can occur due to many reasons- symptoms of mental illness, dementia, delirium, intoxication with alcohol or any other substance, learning disabilities, sedation and more (SCIE, 2024). The impairment can be temporary or permanent. Deciding that someone lacks capacity cannot be judged on the basis of age, appearance, particular diagnosis or other behaviours that may lead to unjustified assumptions about capacity. For example, someone living with a learning disability may lack capacity to make certain decisions, but may retain capacity for other decisions. Therefore, simply having a learning disability cannot be used as the sole rationale for someone lacking capacity for any and all decisions. Similarly, someone displaying extreme distress due to mental illness would not automatically mean they lack capacity. Clinicians should specify what the specific impairment or disturbance is when documenting a capacity assessment and also consider whether someone is likely to regain capacity to make the decision, and when that might be.

3. In relation to a matter if at the material time

Told you we'd come back to the whole 'specific decision' thing. Capacity assessments must be time and decision specific (SCIE, 2024). That means the assessment you make relates to a singular decision (matter) at the time of your assessment (material time). Capacity to make the same decision can fluctuate, even over the course of several hours (CQC, 2011), so it's vital to reassess regularly so that your assessment remains time specific. There's no clear guidance on how frequently reassessments should be made, but the CQC (2011) advises that 'you will need to review assessments and decisions regularly to ensure that they continue to meet the requirements of the Act and the codes of practice'. From my personal experience whilst being detained in hospital under the MCA, as I was judged to not have capacity to make the decision to leave, I was told by security staff that this should be reviewed roughly every hour (which shocked me for 2 reasons- 1 because that feels incredibly frequent and 2 because in this case, it hadn't been reassessed for several days...). If a person is likely to regain capacity, it's important to consider if making the decision can be delayed until such time (CQC, 2011).

Moving on to the actual assessment... A person can be deemed to lack capacity if they fail to meet one or more of the following criteria (, 2024):

  1. Can understand information given that is relevant to the decision

  2. Can retain that information long enough to make a decision

  3. Can use or weigh that information as part of the decision making process

  4. Can communicate their decision by any means

Assessing capacity isn't an exact science, but ultimately comes down to the balance of probabilities- is it more likely that the patient lacks capacity or has capacity to make the decision?

In order to establish the answers to these questions, whoever is assessing capacity may need to provide information about the decision, such as risks and benefits of making a decision, and any alternative options for the decision. The information should be given in a way accessible to the individual, so this could be written down, communicated in simple language or easy read format, or with visual aids (Gov.UK, 2024).

The assessor will need to judge whether that information has been retained and used in making a decision. This may include asking someone to explain the consequences of taking or not taking an action. Even if the informatioon is only retained for a short period of time, this does not mean that the decision cannot be made by the individual (Gov.UK, 2024).

Communication of decisions can take many forms- yet spoken communication is generally the only communication considered. Alternatives could include sign language, writing it down, nodding or shaking your head, or other simple movements like blinking or squeezing a hand (SCIE, 2024). Some people may be non-verbal for many reasons. For example, I am usually verbal, but experience mutism when extremely overwhelmed or in an autistic meltdown/shutdown, and this has meant that I've been deemed not to have capacity on many occassions when I absolutely would've been able to communicate a decision if any alternative form of communication was considered. Similarly, I have conducted a capacity assessment for one of my patients in ICU who was intubated, but was able to write on a whiteboard, and we were able to fully assess her capacity to make the decision to self discharge by considering her communication needs.

There are five key principles that underlie the MCA. These are:

  • A person must be assumed to have capacity until proved otherwise - so someone cannot be assumed to lack capacity purely on the basis of a particular diagnosis, or previous lack of capacity.

  • A person is not treated as lacking capacity until all practicable steps have been taken to support their decision making - people should be encouraged and supported to make the decision for themself, and this continues even if they person is deemed to lack capacity.

  • A person is not assumed to lack capacity on the basis of making an unwise decision - you may not agree with the decision a person wishes to make, but this does not necessarily mean they lack capacity to make that decision.

  • Any decision made on behalf of someone lacking capacity must be made in their best interests

  • Any decision made on behalf of someone lacking capacity must be the least restrictive of the person's rights and freedom of action.

The first 3 principles apply to the process of assessing capacity, whilst the final 2 apply once someone has been deemed not to have capacity.

Deciding what constitutes someone's 'best interests' can be difficult, and the individual should be included as far as possible to end with a decision that is agreeable to them- as ultimately, the outcome of the decision will be impacting on them. It's important to consider the person's past and present wishes (and this may include any statements or advanced decisions written when the person had capacity for the decision), and any values or beliefs that may influence their decision. It may also be relevant to consider the views or opinions of anyone named by the individual to be consulted on the matter, anyone involved in caring for the person, and anyone who holds Lasting Power of Attorney for health and welfare (LPA)- more on this later!

An advanced decision to refuse treatment (ADRT- sometimes known as a living will) cannot be overruled by a capacity decision. This is a legally binding statement outlining an individuals preferences in relation to medical treatment. It is made when an individual has the capacity to make this decision, and hence must be respected, but will only be used if a person lacks capacity at the time of making decisions about medical treatment. An ADRT can be written or verbalised, but must be written, signed and witnessed, and include a statement that it applies even if life is at risk, if it relates to life sustaining treatment (BMA, 2019). Life sustaining treatment is kind of what it says on the tin... any treatment that's considered necessary to preserve life. This could include your typical resuscitation treatments, like CPR or ventilation, but could also include other treatments for conditions that would otherwise not be survivable, like antibiotics for an infection or emergency surgery. Whoever is making decisions about life sustaining treatment in someone's best interests must not be motivated by a desire to bring about death. Which sounds like a weird thing to say, but the MCA specifies it, so I will too (Gov.UK, 2024). ADRTs stil apply if a person is detained under the Mental Health Act (CQC, 2011).

Other statements about care and treatment are not legally binding, but should still be considered as it can be useful to ascertain what decision a person would make if they had the capacity to do so.

Someone can make a lasting power of attorney to appoint a health and welfare attorney- this can be anyone over the age of 18. Once accepted by the courts, the attorney is the lawful decision maker for the individual. This can include decisions about consenting to or refusing life sustaining treatment. Any decisions made must still be in line with the MCA, including consulting others about decisions and acting in the individuals best interests (BMA, 2019).

Liberty Protection Safeguards (LPS) were introduced as an amendment to the MCA, and replace the prior Deprivation of Liberty Safeguards (DoLS). I have to be honest here and say that I didn't even know that DoLS had been replaced! I'm not going into too much detail here, partly because I don't know too much about it myself, but I can say that LPS only applies in England and Wales, and applies to people who are unable to make a decision about care arrangements due to a mental disorder, are under 'continuous supervision and control' and are not free to leave the setting in which they are recieving care or treatment. Typically this will refer to necessary and proportionate restrictions and restraints (physical or chemical) to control behaviour, in a patients best interests. The MCA defines someone as restraining an individual if they use or threaten to use force to enforce a decision which the individual resists, or if they restrict the movement of an individual whether or not the individual resists (MCA, 2024).

You can read more about LPS here. If you want more info on DoLS, it can be found here.

Okay, back to capacity assessments!

As with any aspect of nursing, documentation is vital. If it isn't documented, it didn't happen.

As the significance of the decision being assessed increases (and this will be judged on an individual basis- something that seems like a minor decision to you may be major for someone else), the assessment and decision making process should become more comprehensive. Therefore, the documentation of the process should become more detailed.

According to the CQC (2011), records of assessments should include details of the 2-step assessment- the functional and diagnostic tests-, how the person was helped to make the decision themself, how well the person met the 4 criteria for capacity (understanding, retaining, weighing up and communicating the decision), who was involved in making any decisions if the person lacks capacity, and how, when and why the decision was made. Any relevant information about the person's preferences and wishes should also be noted and documented.

Assessment of mental capacity does not fall solely to psychiatrists, or any other specific mental health professionals. Any HCP can assess capacity, including support workers, nurses, social workers, doctors and more, so the CQC recommends that codes of practice are readily available to facilitate this (CQC, 2011). Further, all staff caring for someone are encouraged to partake in assessing capacity, rather than relying on specialist staff. However, some complex or major decisions may require input from someone who knows the patient well, such as a GP, or a specialist like a psychologust or psychiatrist (SCIE, 2024).

Failure to accurately assess capacity not only affects patients, but can also affect service providers. The CQC will take failure to comply with and apply the MCA into account during inspections when assessing compliance and regulation (CQC, 2011).

Finally, a personal note from me... (trigger warning for suicide)

A challenge for Crisis Teams and other mental health clinicians (I'm pretty sure mine look at this blog- ain't no way I'm getting this many views from Oxford without someone from mental health services checking in on me...) - stop telling people they have capacity to end their life. It's callous, irresponsible, unsafe, and your duty of care should supercede someone's capacity if they have disclosed something to you that indicates harm to themself or others. Do better, please and thank you.

Thank you so much for reading, I hope this was helpful! I can't explain my sudden affinity for making memes instead of using words, but I enjoyed it nonetheless. As always, please let me know your thoughts, opinions, suggestions, and any ideas for future posts!


Christie x


Gov.UK (2024) Mental Capacity Act 2005. Available at: (Accessed 17 Feb 2024)

CQC (2011) The Mental Capacity Act 2005: Guidance for providers. Available at: (Accessed 17 Feb 2024)

BMA (2019) Best interests decision-making for adults who lack capacity: a toolkit for doctors working in England and Wales. Available at: (Accessed 19 Feb 2024)

SCIE (2022b) What are Liberty Protection Safeguards? Available at: (Accessed 19 Feb 2024)

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