The US has for years been the world’s biggest jailer. Now prison watchdogs are highlighting the widespread use of solitary confinement, warning about the physical and mental toll that the practice exerts on inmates.

More than 122,000 people are being held in solitary confinement at any one time in US prisons and jails, a report by Unlock The Box and Solitary Watch based on 2019 data says. Inmates separated from the general prison population routinely face at least 22 hours alone each day.

And in many cases, people are held in solitary confinement - variously known as ‘restrictive housing’ or ‘administrative segregation’ by corrections authorities - for weeks, months or even years. Psychiatrists say prolonged isolation has a devastating impact on prisoners’ mental health, and United Nations experts say solitary confinement beyond 15 days is torture.

'The Box', a new film by Al Jazeera's Fault Lines, highlights the case of Dennis Wayne Hope, a prisoner who was held in solitary confinement for 27 years and was only released into the general prison population after a legal challenge.

In this episode of The Stream, we ask why so many people in US prisons and jails face protracted spells without meaningful human contact and look at efforts to challenge the practice.