Mental Health Act 1983

The MHA 1983 framework: civil detention (Part 2) for those with a mental disorder posing risks to themselves or others; criminal detention (Part 3) for mentally disordered offenders. Most common sections: s.2 (28 days for assessment), s.3 (6 months renewable for treatment), s.4 (72 hours emergency), s.135 (warrant entry from a private home), s.136 (place of safety from a public place), s.117 (free aftercare after s.3). Mental Health Tribunal review is automatic at first detention; renewal periods give further review rights. The Mental Health Act 2025 received Royal Assent on 18 December 2025 and amends the 1983 Act, but only sections 51 and 52 commenced on 6 April 2026 — the substantive reforms, including the nominated person and advance choice documents, are not yet in force.

In practice, what matters to a patient and their family is who has to agree before someone can be detained, and what happens next. A civil detention needs an application by an Approved Mental Health Professional (or, less commonly, the nearest relative) supported by two medical recommendations, one from a doctor approved under section 12 who should where possible have prior knowledge of the patient. That structure is a safeguard: if the paperwork is defective, the detention is unlawful.

Worked example: Tom is detained under section 2 for assessment after a mental health crisis. The maximum period is 28 days and it cannot be renewed — the team must either discharge him, arrange informal admission, or apply for section 3. He has 14 days from the start of the detention to apply to the Tribunal, and free legal representation is available regardless of his means. His mother, as nearest relative, can also request his discharge by giving 72 hours' written notice to the hospital managers, though the responsible clinician can block it by issuing a barring report. When Tom is later detained under section 3, he becomes entitled to free section 117 aftercare on discharge, which cannot be charged for.

The misconceptions cause avoidable distress. Being detained does not mean losing the right to refuse everything: Part 4 governs treatment for mental disorder, and after three months a second opinion appointed doctor must certify treatment the patient does not consent to. Treatment for unrelated physical illness is not covered by the Act at all and needs consent or a capacity assessment. Section 136 is a police power to remove someone from a public place to a place of safety, not an arrest, and it is time-limited. And a voluntary or informal patient is free to leave, though staff may use short holding powers under section 5 if they judge that an application should be made.

The Act generates section 117 aftercare, the right to an independent mental health advocate, and review by the Mental Health Tribunal; where the issue is capacity rather than compulsion, the Mental Capacity Act 2005 applies instead. Read our guides to the Mental Health Act and where the 2025 reforms stand.