For most jurisdictions, involuntary commitment is applied to individuals believed to be experiencing a mental illness that impairs their ability to reason to such an extent that the agents of the law, state, or courts determine that decisions will be made for the individual under a legal framework. In some jurisdictions, this is a proceeding distinct from being found incompetent. Involuntary commitment is used in some degree for each of the following although different jurisdictions have different criteria. Some jurisdictions limit involuntary treatment to individuals who meet statutory criteria for presenting a danger to self or others. Other jurisdictions have broader criteria. The legal process by which commitment takes place varies between jurisdictions. Some jurisdictions have a formal court hearing where testimony and other evidence may also be submitted and the subject of the hearing is typically entitled to legal counsel and may challenge a commitment order through habeas corpus.^[4] Other jurisdictions have delegated these power to physicians,^[2] though may provide an appeal process that involves the judiciary but may also involve physicians.^[c] For example, in the UK a mental health tribunal consists of a judge, a medical member, and a lay representative.^[d]

Training is gradually becoming available in mental health first aid to equip community members such as teachers, school administrators, police officers, and medical workers with training in recognizing, and authority in managing, situations where involuntary evaluations of behavior are applicable under law.^[7] The extension of first aid training to cover mental health problems and crises is a quite recent development.^[8][9] A mental health first aid training course was developed in Australia in 2001 and has been found to improve assistance provided to persons with an alleged mental illness or mental health crisis. This form of training has now spread to a number of other countries (Canada, Finland, Hong Kong, Ireland, Singapore, Scotland, England, Wales, and the United States).^[10] Mental health triage may be used in an emergency room to make a determination about potential risk and apply treatment protocols.

Observation is sometimes used to determine whether a person warrants involuntary commitment. It is not always clear on a relatively brief examination whether a person should be committed.

Austria, Belgium, Germany, Israel, the Netherlands, Northern Ireland, the Republic of Ireland, Russia, Taiwan, Ontario (Canada), and the United States have adopted commitment criteria based on the presumed danger of the defendant to self or to others.^[11]

People with suicidal thoughts may act on these impulses and harm or kill themselves.

People with psychosis are occasionally driven by their delusions or hallucinations to harm themselves or others. Research has found that those with schizophrenia are between 3.4 and 7.4 times more likely to engage in violent behaviour than members of the general public. ^[12] However, because other confounding factors such as childhood adversity and poverty are correlated with both schizophrenia and violence it can be difficult to determine whether this effect is due to schizophrenia or other factors. In an attempt to avoid these confounding factors, researchers have tried comparing the rates of violence amongst people diagnosed with schizophrenia to their siblings in a similar manner to twin studies. In these studies people with schizophrenia are found to be between 1.3 and 1.8 times more likely to engage in violent behaviour.^[12]

People with certain types of personality disorders can occasionally present a danger to themselves or others.^[13]

This concern has found expression in the standards for involuntary commitment in every US state and in other countries as the danger to self or others standard, sometimes supplemented by the requirement that the danger be imminent. In some jurisdictions,^[which?] the danger to self or others standard has been broadened in recent years to include need-for-treatment criteria such as "gravely disabled".^[14]

Starting in the 1960s, there has been a worldwide trend toward moving psychiatric patients from hospital settings to less restricting settings in the community, a shift known as "deinstitutionalization". Because the shift was typically not accompanied by a commensurate development of community-based services, critics say that deinstitutionalization has led to large numbers of people who would once have been inpatients as instead being incarcerated or becoming homeless.^[15] In some jurisdictions, laws authorizing court-ordered outpatient treatment have been passed in an effort to compel individuals with chronic, untreated severe mental illness to take psychiatric medication while living outside the hospital (e.g. Laura's Law, Kendra's Law).^[16][17]

In a study of 269 patients from Vermont State Hospital done by Courtenay M. Harding and associates, about two-thirds of the ex-patients did well after deinstitutionalization.^[18]

In 1838, France enacted a law to regulate both the admissions into asylums and asylum services across the country. Édouard Séguin developed a systematic approach for training individuals with mental deficiencies,^[19] and, in 1839, he opened the first school for intellectually disabled people. His method of treatment was based on the idea that intellectually disabled people did not suffer from disease.^[20]

In the United Kingdom, provision for the care of the mentally ill began in the early 19th century with a state-led effort. Public mental asylums were established in Britain after the passing of the 1808 County Asylums Act. This empowered magistrates to build rate-supported asylums in every county to house the many "pauper lunatics". Nine counties first applied, and the first public asylum opened in 1812 in Nottinghamshire. Parliamentary Committees were established to investigate abuses at private madhouses like Bethlem Hospital - its officers were eventually dismissed and national attention was focused on the routine use of bars, chains and handcuffs and the filthy conditions in which the inmates lived. However, it was not until 1828 that the newly appointed Commissioners in Lunacy were empowered to license and supervise private asylums.

The Lunacy Act 1845 was a landmark in the treatment of the mentally ill, as it explicitly changed the status of mentally ill people to patients who required treatment. The Act created the Lunacy Commission, headed by Lord Shaftesbury, focusing on reform of the legislation concerning lunacy.^[21] The commission consisted of eleven Metropolitan Commissioners who were required to carry out the provisions of the Act;^{[22][full citation needed]} the compulsory construction of asylums in every county, with regular inspections on behalf of the Home Secretary. All asylums were required to have written regulations and to have a resident qualified physician.^[22] A national body for asylum superintendents - the Medico-Psychological Association - was established in 1866 under the Presidency of William A. F. Browne, although the body appeared in an earlier form in 1841.^[23]

At the turn of the century, England and France combined had only a few hundred individuals in asylums.^[24] By the late 1890s and early 1900s, those so detained had risen to the hundreds of thousands. However, the idea that mental illness could be ameliorated through institutionalization was soon disappointed.^[25] Psychiatrists were pressured by an ever-increasing patient population.^[25] The average number of patients in asylums kept increasing.^[25] Asylums were quickly becoming almost indistinguishable from custodial institutions,^[26] and the reputation of psychiatry in the medical world had was at an extreme low.^[27]

Sectioning is now regulated by the Mental Health Act 2007 in England and Wales, the Mental Health (Care and Treatment) (Scotland) Act 2003 in Scotland and other legislation in Northern Ireland.

In the United States, the erection of state asylums began with the first law for the creation of one in New York, passed in 1842. The Utica State Hospital was opened approximately in 1850. The creation of this hospital, as of many others, was largely the work of Dorothea Lynde Dix, whose philanthropic efforts extended over many states, and in Europe as far as Constantinople. Many state hospitals in the United States were built in the 1850s and 1860s on the Kirkbride Plan, an architectural style meant to have curative effect.^[28]

In the United States and most other developed societies, severe restrictions have been placed on the circumstances under which a person may be committed or treated against their will as such actions have been ruled by the United States Supreme Court and other national legislative bodies as a violation of civil rights and/or human rights. The Supreme Court case O'Connor v. Donaldson established that the mere presence of mental illness and the necessity for treatment are not sufficient by themselves to justify involuntary commitment, if the patient is capable of surviving in freedom and does not present a danger of harm to themselves or others. Criteria for involuntary commitment are generally set by the individual states, and often have both short- and long-term types of commitment. Short-term commitment tends to be a few days or less, requiring an examination by a medical professional, while longer-term commitment typically requires a court hearing, or sentencing as part of a criminal trial. Indefinite commitment is rare and is usually reserved for individuals who are violent or present an ongoing danger to themselves and others.

New York City officials under several administrations have implemented programs involving the involuntary hospitalization of people with mental illnesses in the city.^[29] Some of these policies have involved reinterpreting the standard of "harm to themselves or others" to include neglecting their own well-being or posing a harm to themselves or others in the future. In 1987–88, a homeless woman named Joyce Brown worked with the New York Civil Liberties Union to challenge her forced hospitalization under a new Mayor Ed Koch administration program. The trial, which attracted significant media attention, ended in her favor, and while the city won on appeal she was ultimately released after a subsequent case determined she could not be forcibly medicated.^[30][31] In 2022, Mayor Eric Adams announced a similar compulsory hospitalization program, relying on similar legal interpretations.^[32][33]

Historically, until the mid-1960s in most jurisdictions in the United States, all committals to public psychiatric facilities and most committals to private ones were involuntary. Since then, there have been alternating trends towards the abolition or substantial reduction of involuntary commitment,^[34] a trend known as deinstitutionalisation. In many currents, individuals can voluntarily admit themselves to a mental health hospital and may have more rights than those who are involuntarily committed. This practice is referred to as voluntary commitment.

In the United States, Kansas v. Hendricks established the procedures for a long-term or indefinite form of commitment applicable to people convicted of some sexual offences.^[35]

United Nations General Assembly Resolution 46/119, "Principles for the Protection of Persons with Mental Illness and the Improvement of Mental Health Care", is a non-binding resolution advocating certain broadly drawn procedures for the carrying out of involuntary commitment.^[36] These principles have been used in many countries^[which?] where local laws have been revised or new ones implemented. The UN runs programs in some countries to assist in this process.^[37]