The 1983 Act provides a legal framework to authorise the detention and compulsory treatment of people who have a mental disorder and are considered at risk of harm to themselves or others. The 1983 Act is structured into ten parts.
	Part 1 sets out the application of the 1983 Act, i.e. "to the reception, care and treatment of mentally disordered patients". Powers for compulsory admission under the 1983 Act are set out in Part 2 and Part 3 of the 1983 Act. The majority of the Act amends these parts of the 1983 Act. Part 2 deals with patients who are liable to be detained in hospital and who are not subject to the 1983 Act as a consequence of any involvement with the criminal justice system. These patients are generally referred to as ‘civil patients’. Part 3 is concerned with patients who are involved in criminal proceedings or are under sentence. The majority of people detained under the 1983 Act are detained under Part 2, with over two-thirds (70.8%) of people recorded as in detention in hospital on 31st March 2024 being detained under Part 2, and less than a third (29.2%) detained under Part 3. 1 The Ministry of Justice leads on the reforms to Part 3 of the 1983 Act, (as introduced by the Act) and further detail on Part 3 is set out below.
	The Act also makes amendments to:
Part 4 of the 1983 Act, which provides for the treatment of patients detained in hospital, or of community patients who are liable to be so detained;
Part 8 of the 1983 Act, which contains miscellaneous functions of Local Authorities (i.e. the approval of Approved Mental Health Act Professionals, the provision of after-care, and the right for Local Authority staff to visit patients in certain circumstances), and of the Secretary of State (including the requirement to produce a Code of Practice for the 1983 Act, and certain duties of the regulatory authority, the Care Quality Commission in England and in Wales, the Care Inspectorate Wales);
Part 9 of the 1983 Act, which provides for offences under the 1983 Act; and
Part 10 of the 1983 Act, which contains miscellaneous provisions.
	The 1983 Act was last amended in 2007, amongst other changes these amendments introduced Community Treatment Orders, Independent Mental Health Advocates and amended the detention criteria with the effect that someone cannot be detained for treatment unless appropriate treatment is available.
The Mental Health Act 1983 (the 1983 Act)