There are various pros and cons to using solitary confinement. Those in favor of the practice mainly cite its importance regarding the protection and safety of inmates, prison staff and the general public. An inmate who is a child molester, or who has killed gang members, may be at high risk of being injured or killed by fellow prisoners; being placed in segregation can provide him protection. Or a prisoner who has attacked her fellow inmates and staff may be placed in lockdown to protect these people.
Solitary confinement also presumably makes it more difficult for a prisoner to escape, providing an added layer of security for the public from high-risk offenders. Additionally, some proponents argue prison staff needs the disciplinary option of solitary confinement to aid with unruly inmates. And others note sometimes it's simply necessary to manage cell space [sources: Connect Us, Manson].
Placing someone in isolation isn't necessarily a terrible practice, experts say. But it must be employed sparingly and only for very short periods of time. The United Nations, for one, says no one should be held in segregation for more than 15 days.
A study on prisoners held in solitary confinement at Pelican Bay prison in California found that people held in lockdown for long periods of time often suffer from a myriad of mental health issues, including depression, apathy, hallucinations, panic attacks, paranoia and hypersensitivity to external stimuli. They also may develop difficulties with thinking, concentration and memory; become angry and violent; have trouble sleeping or have nightmares; and suffer from dizziness, heart palpitations and perspiring hands. These symptoms may remain long after the person is released or put back in the general prison population [sources: Moore, Breslow, The Guardian, Penal Reform].
Numerous studies show that prisoners held in solitary confinement have higher rates of self-mutilation and suicide than those in traditional cells. In a 1999 to 2004 study of California's prison system, for example, nearly half of all inmate suicides were committed by those in segregation. And an analysis of nearly 250,000 New York City prisoner medical records from 2010 to 2013 showed 53.3 percent of inmates held in lockdown committed acts of self-harm and 45 percent committed acts of potentially fatal self-harm, even though this group comprised only 7.3 percent of admissions [sources: Breslow, Kaba, et al].
In addition to the psychological toll on prisoners, there's also a financial toll on taxpayers. In the federal system, it costs $78,000 per year to house one inmate in solitary confinement versus about $58,000 for a regular prisoner [sources: Johnson and Chappell, Infographic World].