Mental health law and compulsory treatment

The Mental Health Act

The Mental Health Act 1983 is the law that allows people living in England and Wales who have a ‘mental disorder’ to be admitted, detained and treated in hospital without their consent – either for their own health or safety, or for the protection of other people.

The Act was amended by the Mental Health Act 2007 and was slightly amended again by the Health and Social Care Act 2012. The Mental Health Act is the law that people who experience the symptoms of psychosis are most likely to encounter – the Mental Health Act allows treatment to be given regardless of whether people have the capacity to consent. Visit the Mental Health Act page for more information.

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The Mental Capacity Act

The Mental Capacity Act 2005 spells out different legal ways of making a wide range of decisions on behalf of someone aged over 16 when that person is unable to make a decision for him or herself because they 'lack capacity'. People may lack capacity for different reasons – because they have dementia, a brain injury or a learning disability, for example.

The Mental Capacity Act defines ‘lacking capacity’ and describes how to determine whether someone is lacking capacity at any particular time.

An individual is considered to lack capacity to make a specific decision if they are: 

1) unable to understand information relevant to the decision; or
2) unable to retain that information; or
3) unable to weigh up and use the information to make the decision; or

4) unable to communicate their decision.

An individual only has to meet one of these four criteria to be considered to lack the capacity to make a decision.

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Decisions about treatment and care

People who experience the symptoms of psychosis may, because of the effects of those symptoms, sometimes lack capacity to make decisions about their treatment and care. But case law stipulates that people who lack capacity because of a mental illness should be treated for that illness under the Mental Health Act.

However, the Mental Capacity Act might be used to give treatment for physical health problems to someone who lacks capacity because of a mental illness – if someone who was experiencing psychosis needed hospital-based treatment for pneumonia, for example.

The Mental Capacity Act can only be used to give treatment to somebody without their consent if that person is assessed as lacking capacity at that particular time, and if treatment would be in their 'best interests.'

This means that any decision reached on behalf of the individual who lacks capacity must be the best course of action for him or her.

Mostly, the doctor who will be responsible for giving the medical treatment will be responsible for making the 'best interests' decision and in order to reach this decision, he or she must work through a process and statutory checklist which is contained in Section 4 of the Mental Capacity Act. 

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Deprivation of liberty safeguards procedure

If hospital staff want to detain someone for treatment under the Mental Capacity Act, they need to use the 'Deprivation of liberty safeguards' procedure. This process aims to protect vulnerable people by ensuring that any decision to deprive someone of their liberty is taken following a proper legal process.

A hospital (or care home) must apply to the local authority for authorisation to deprive someone who lacks capacity of their liberty. Two different professionals are then appointed to carry out assessments to find out if six different criteria are met. One of the criteria is that the person lacks capacity to make a decision about the care or treatment they will receive in hospital or in a care home. Another is that deprivation of liberty is in the best interests of the individual.

If all six criteria are met, authorisation will be given and the person can be legally deprived of their liberty by the hospital or care home. In 2013-2014, the majority of applications under this process were for people who have dementia.

The deprivation of liberty safeguard process should not be used to detain someone for treatment for a mental health problem: the Mental Health Act should be used to detain someone for treatment for a 'mental disorder'.

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Mental Capacity Act advance decisions

The Mental Capacity Act (Sections 24, 25 and 26) specifically allows people to make an 'advance decision' to refuse treatment at a future time when they lack capacity (though this can be over-ruled in some instances). It also allows people to make a written statement about their wishes and preferences, should they lose capacity. These statements are not legally binding but should be considered when best interests decisions are being taken. The law also enables people to appoint 'an attorney' to make decisions for them if they lose capacity in future.

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Reviewing the Mental Capacity Act

A House of Lords Select Committee was set up to investigate whether the Mental Capacity Act is working effectively.

The committee's report was published in March 2014 and found that many health and social care professionals are not using the Act as they should in their everyday work – capacity assessments are often not carried out, for example – and recommended that an independent organisation be set up to promote and oversee the implementation of the Act.

The committee was also critical of the Deprivation of liberty safeguards, saying they are complicated, poorly understood and not fit for purpose – and called for a better system to protect vulnerable people held in care homes or hospitals.

In June 2014, the government published: Valuing every voice, respecting every right: making the case for the Mental Capacity Act 2005. This document includes recommendations for the future, including the establishment of a new Mental Capacity Advisory Board to raise awareness of the legislation among professionals and families. The government has asked the Law Commission to consider improvements that could be made to the Deprivation of liberty safeguards system. The Law Commission plans to publish recommendations for reform and a draft Bill in the summer of 2017.

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Codes of Practice

There are Codes of Practice for the Mental Health Act, the Mental Capacity Act and the Deprivation of liberty safeguards. These Codes of Practice give guidance about good practice and how to act within the law. Mental health professionals have to take account of them in their work. A revised and updated Mental Health Act Code of Practice was published in January 2015 and comes into force on 1 April 2015. The new iteration reflects changes in the law and developments in professional practice that have happened since the last update. 

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Independent mental capacity advocates and independent mental health advocates

Local authorities have a duty to arrange an independent mental capacity advocate (IMCA) service to provide help and support to people who are subject to the Mental Capacity Act 2005.

An IMCA will support and represent people who lack capacity and do not have family or friends to represent them when decisions are being made about their health or social care, or when hospitals or care homes are applying for authorisation to deprive them of their liberty.

Local authorities also have a duty to arrange an independent mental health advocate (IMHA) service to provide help and support to people detained or treated under the 1983 Mental Health Act.



This page was last updated 15 February 2015
Links checked 7 July 2016


Mental Health Act Code of Practice, updated version, January 2015

Reference Guide to the Mental Health Act 1983
published by the Department of Health, 2015

Mental Capacity Act Code of Practice

Mental Capacity Act 2005 Deprivation of liberty safeguards – Code of Practice to supplement the main Mental Capacity Act 2005 Code of Practice

Best interests: Guidance on determining the best interests of adults who lack the capacity to make a decision (or decisions) for themselves (England and Wales)

A report published by the Professional Practice Board of the British Psychological Society.

Other useful websites

Mental Capacity Act - making decisions


Mental Health Act 1983

Mental Capacity Act 2005

Mental Health Act 2007
(amendments to the Mental Health Act 1983 and the Mental Capacity Act 2005)

Health and Social Care Act 2012