Solitary confinement constitutes torture and causes lasting mental harm

The claim

Solitary confinement — the practice of confining a person in a small cell for 22 to 24 hours per day, with minimal human contact, often for weeks, months, or years — is defended by corrections administrators as a necessary security measure for the most dangerous or disruptive prisoners. Proponents argue that isolation protects staff and general-population inmates from assault, that it is a legitimate last resort for those who cannot be safely housed otherwise, and that the discomfort it produces is proportionate to the threat posed. On this account, solitary is an unfortunate but necessary tool — not torture.

The structural claim is the inverse: isolation at this duration and intensity is not a neutral administrative classification but a form of psychological torture. It produces a recognizable and severe psychiatric syndrome, causes lasting neurological and psychological damage, is applied disproportionately to mentally ill prisoners (making it simultaneously a response to and a cause of mental illness in prison), and is not justified by the security outcomes it is claimed to produce. The international consensus — codified in the UN Nelson Mandela Rules — is that solitary exceeding 15 days constitutes cruel, inhuman, or degrading treatment regardless of the individual’s offense.

The mechanism

Humans are social animals with neurological systems calibrated to expect sensory input, human interaction, and environmental variety. Prolonged removal of these inputs does not produce a neutral baseline state — it produces active psychiatric deterioration. The mechanism is not metaphorical.

Sensory deprivation and neurological effects: Decades of sensory deprivation research, beginning with McGill University experiments in the 1950s (Bexton, Heron, Scott 1954), established that healthy adults placed in low-stimulation environments develop perceptual distortions, hallucinations, and cognitive impairment within hours. Solitary confinement replicates many features of experimental sensory deprivation, but extends them over months or years, inside a coercive institution, with no informed consent and no ability to exit. The neurological result is a form of stress-induced cortical dysfunction: the prefrontal cortex — governing executive function, emotional regulation, and social cognition — is particularly vulnerable to chronic isolation stress. Craig Haney’s work documenting hyperresponsivity, hypersensitivity to stimuli, and cognitive fragmentation in solitary prisoners maps directly onto this mechanism.

The specific psychiatric syndrome: Stuart Grassian, a Harvard Medical School psychiatrist, documented in his landmark 1983 American Journal of Psychiatry paper a distinct and consistent psychiatric syndrome among solitary prisoners at Walpole State Prison. All 14 prisoners in the initial sample — regardless of prior psychiatric history — exhibited: hypersensitivity to external stimuli (light, sound, smell), perceptual distortions and illusions, paranoid ideation, difficulties with concentration and memory, intrusive obsessive thoughts, hypersensitivity to the limited stimuli available (excessive preoccupation with a crack in the wall), and aggressive fantasies. Grassian’s expanded 2006 review of the literature confirmed the syndrome across settings, countries, and decades, and noted that it overlaps symptomatically with delirium and can include frank psychosis.

The syndrome is not merely discomfort. It is not analogous to the unpleasantness of a restricted diet or reduced recreation. It is a psychiatric injury produced by the conditions of confinement itself.

The evidence

Grassian’s clinical documentation (1983, 2006): Grassian’s methodology involved structured psychiatric interviews with prisoners in solitary at Walpole. His 1983 paper, published in the American Journal of Psychiatry, is the first systematic clinical description of what became known as the “SHU syndrome” (after Security Housing Units). His 2006 review in the Washington University Journal of Law and Policy examined subsequent research from US supermax facilities, Australian high-security units, and international contexts, and concluded: “Solitary confinement can cause severe psychiatric harm.” The symptom cluster he identified — which he formally characterized as “reduced impulse control, hypersensitivity to stimuli, cognitive dysfunction, and paranoia” — has since been documented by independent researchers across dozens of institutions.

Haney’s systematic research: Craig Haney, a psychology professor at UC Santa Cruz, conducted the most comprehensive empirical study of a US supermax population, examining 100 prisoners at Pelican Bay State Prison’s Security Housing Unit in 1993. Haney found that 91% reported anxiety and nervousness; 70% reported feelings of rage; 84% reported problems with concentration; 88% reported headaches; 41% reported hallucinations; 27% reported perceptual distortions. These rates are dramatically elevated above general prison population baselines. Haney’s subsequent work has tracked prisoners after release from supermax and documented persistent psychiatric effects — elevated paranoia, social anxiety, and hyperresponsiveness — sometimes lasting years after release. His 2003 paper in Crime and Delinquency reviewed the evidence base and concluded that the weight of clinical and empirical research “makes a compelling case that isolation constitutes a unique and serious form of psychological suffering.”

Disproportionate application to mentally ill prisoners: In a finding that the UN Special Rapporteur on Torture has repeatedly highlighted as self-evidently cruel, mentally ill prisoners are placed in solitary at rates 3 to 8 times higher than the general prison population, despite the fact that the psychiatric effects of isolation are most severe in people with pre-existing mental illness. Prisoners with schizophrenia, bipolar disorder, and major depression placed in solitary confinement experience psychotic decompensation, suicide attempts, and self-mutilation at rates far exceeding any other custodial setting. The American Psychiatric Association’s 2012 position statement called for an absolute prohibition on solitary confinement for prisoners with serious mental illness.

The Colorado natural experiment: Between 2011 and 2017, the Colorado Department of Corrections reduced its solitary confinement population by approximately 85% under the direction of Rick Raemisch, the executive director. The reforms were systematic: new classification criteria requiring mental health screening, step-down programming rather than abrupt release, and a prohibition on placing prisoners with serious mental illness in isolation. A 2017 Pew Charitable Trusts review of the Colorado reforms found no increase in overall prison violence. Assaults on staff did not rise; major disturbances did not increase. The security justification for mass isolation was not supported by the Colorado evidence.

Supermax and violence rates: Daniel Mears and Jamie Watson’s 2006 research on supermax prisons, published in Crime & Delinquency, examined the empirical evidence for the claim that supermax facilities reduce prison violence systemwide. Their analysis found that the evidence was “largely lacking” — most states could not demonstrate that opening a supermax facility reduced violence in their broader prison system. States with higher supermax capacity did not have lower rates of prison assaults than those with less. The specific violence-reduction claim that is the primary policy justification for solitary confinement is not supported by the comparative evidence across US state prison systems.

UN Nelson Mandela Rules: The 2015 revision of the United Nations Standard Minimum Rules for the Treatment of Prisoners — renamed the Nelson Mandela Rules — codified the global human rights consensus. Rule 44 defines prolonged solitary confinement (exceeding 15 consecutive days) as cruel, inhuman, or degrading treatment or punishment. Rule 45 prohibits the imposition of solitary on prisoners with mental or physical disabilities when their conditions would be exacerbated by such measures. These rules represent the consensus of the UN General Assembly, passed by resolution A/RES/70/175, and are considered authoritative in international human rights law even without treaty-level binding force.

Scale in the US: The Association of State Correctional Administrators’ 2019 survey, conducted in collaboration with Yale Law School, estimated that approximately 61,000 people were held in “restricted housing” in state and federal prisons — a figure that does not include local jails. Estimates incorporating jails range to approximately 80,000 people on any given day. The US holds more people in solitary confinement in absolute terms than any other country for which data is available, and uses it for far longer durations: placements of multiple years or decades are documented in the US; the Pelican Bay SHU held some prisoners in isolation for over 20 consecutive years.

Who benefits

Corrections officers unions — particularly the California Correctional Peace Officers Association (CCPOA) and analogous organizations in Texas, New York, and other large prison states — have historically opposed reforms to solitary confinement classification. Solitary provides an administrative tool that simplifies management of difficult prisoners and protects officers from assault by the most volatile individuals; unions have argued against restrictions on these grounds. The CCPOA spent approximately $8 million on California political campaigns in the 2010 election cycle and has consistently lobbied against criminal justice reforms that reduce prison populations or restrict disciplinary tools.

State Departments of Corrections have institutional interests in maintaining solitary as a management tool regardless of its psychiatric effects on prisoners. Reclassification requires investment in programming, mental health staffing, and step-down units — costs that fall in the current budget cycle, while the benefits (reduced recidivism, lower lifetime corrections costs for prisoners who leave prison without supermax-induced psychiatric injury) accrue over years.

Private prison companies including CoreCivic and GEO Group operate several supermax or high-security facilities under state contracts. Their contracts are typically structured per-diem by bed, not by outcome, creating no financial incentive to invest in programming that reduces isolation and potential incentive to maintain high-security classifications that justify higher per-diem rates.

The counter

The structural critique of solitary confinement does not seriously grapple with a genuine operational problem: prisons contain a small number of people who have committed extreme violence against other prisoners and staff, and who present ongoing credible threats. The question of what to do with a prisoner who has killed two cellmates is not answered by citing Norway’s statistics. Corrections administrators are not simply wrong to note that some form of separation from the general population is necessary for some individuals.

The strongest version of the pro-solitary position is not a defense of the US status quo — 80,000 people in indefinite isolation, including thousands with serious mental illness — but a defense of time-limited separation with genuine step-down programming, mental health oversight, and meaningful human contact preserved even during separation. The German “separation” model (Einzelhaft), for instance, involves reduced contact with the general population but guarantees prisoner access to mental health services, exercise, and regular staff interaction, and is subject to judicial review.

The evidence also does not establish that short-duration separation (under 15 days, with preserved human contact) causes the psychiatric syndrome Grassian documented — his and Haney’s evidence primarily concerns extended isolation of weeks to years. The UN’s 15-day threshold attempts to distinguish legitimate short-term separation from the torture category, and this distinction has some empirical grounding.

Where the evidence does not support the pro-solitary position is in the claim that US-scale, US-duration solitary confinement is an effective violence-reduction tool. Mears and Watson’s finding that supermax capacity does not predict lower systemic violence, combined with Colorado’s natural experiment, undermines the central security justification. The practice as actually implemented in the US is not a reluctant last resort for the irreducibly dangerous — it is a default management tool applied to the disruptive, the mentally ill, and the administratively inconvenient, at a scale and duration that produces documented psychiatric injury.

References

Grassian, S. (1983). Psychopathological effects of solitary confinement. American Journal of Psychiatry, 140(11), 1450–1454. https://doi.org/10.1176/ajp.140.11.1450

Grassian, S. (2006). Psychiatric effects of solitary confinement. Washington University Journal of Law and Policy, 22, 325–383.

Haney, C. (2003). Mental health issues in long-term solitary and “supermax” confinement. Crime & Delinquency, 49(1), 124–156. https://doi.org/10.1177/0011128702239239

Haney, C. (2018). Restricting the use of solitary confinement. Annual Review of Criminology, 1, 285–310. https://doi.org/10.1146/annurev-criminol-032317-092326

Mears, D. P., & Watson, J. (2006). Towards a fair and balanced assessment of supermax prisons. Justice Quarterly, 23(2), 232–270. https://doi.org/10.1080/07418820600688867

Pew Charitable Trusts. (2017). Colorado’s turn away from solitary confinement. Pew Charitable Trusts. https://www.pewtrusts.org/en/research-and-analysis/reports/2017/10/colorados-turn-away-from-solitary-confinement

Shalev, S. (2008). A sourcebook on solitary confinement. Mannheim Centre for Criminology, London School of Economics.

Smith, P. S. (2006). The effects of solitary confinement on prison inmates: A brief history and review of the literature. Crime and Justice, 34(1), 441–528. https://doi.org/10.1086/500626

United Nations. (2015). United Nations standard minimum rules for the treatment of prisoners (the Nelson Mandela Rules). A/RES/70/175. https://www.unodc.org/unodc/en/justice-and-prison-reform/mandela-rules.html

Vera Institute of Justice. (2022). Solitary confinement is never the answer. Vera Institute of Justice. https://www.vera.org/publications/solitary-confinement-is-never-the-answer