What is solitary confinement? why are prisoners subjected to solitary confinement and what effects does it have on them?

Solitary confinement holds an individual prisoner in a cell alone, with no contact with other inmates.  Prisoners are subjected to solitary confinement if they are considered to be a dangerous threat to others in the general prison population, especially as an added level of punishment if they have acted violently while in prison.  

Solitary confinement takes a toll on a prisoner's mental health.   Dealing appropriately with mental illness continues to be a problem in prisons in the United States.  A 2010 article in The Journal of the American Academy of Psychiatry and the Law described how solitary confinement poses a challenge for medical ethics.  The authors summarize:  "In recent years, prison officials have increasingly turned to solitary confinement as a way to manage difficult or dangerous prisoners. Many of the prisoners subjected to isolation, which can extend for years, have serious mental illness, and the conditions of solitary confinement can exacerbate their symptoms or provoke recurrence."