(Seth Wenig/AP)

Kalief Browder spent a significant portion of his short life in jail, and most of his time behind bars was spent in solitary confinement. Browder had never been convicted of a crime, but he was accused of robbing someone, and that was enough for him to spend three of his years at Rikers Island in New York.

His story was told by Jennifer Gonnerman in an article in the New Yorker in October outlining Browder’s journey through a frayed criminal justice system. Browder described long stretches of isolation in solitary confinement, and he told her he was abused by inmates and corrections officers inside Rikers. Gonnerman later obtained and published footage capturing such violence.

“Being home is way better than being in jail,” Browder told Gonnerman after he was released. “But in my mind right now I feel like I’m still in jail, because I’m still feeling the side effects from what happened in there.”

Gonnerman reported on Sunday that Browder had committed suicide the day before. His family left no doubt about why they believe Browder took his own life.

“After fighting so hard to get out of jail — and then fighting on the outside to restart his life — he ultimately was unable to overcome his own pain and torment which emanated from his experiences in solitary confinement,” Browder’s family said in a statement.

[Kalief Browder’s suicide and the high cost of violence and delay at Rikers]

Solitary confinement is also known by other names — including isolation, punitive segregation, restricted housing — but the basic idea is generally the same: An inmate is removed from the larger inmate population for some period of time. Each year, tens of thousands of people are placed in solitary confinement, many of them placed in small, narrow rooms for long stretches.

This can be used as a temporary measure to protect that inmate, other inmates or prison employees, or as a punishment for some sort of infraction. Some inmates are isolated for violent actions or threats, but experts say many people are also sent to solitary for doing things like talking back. Regardless of the cause, the forced segregation takes someone who is already imprisoned and removes almost any human contact or interaction from their life.

The effects of solitary are hard to overstate. Experts say it can have catastrophic psychological effects, particularly on younger people or those with mental health issues. “The level of suffering and despair in many of these [solitary confinement] units is palpable and profound,” Craig Haney, a psychology professor at the University of California Santa Cruz who has studied the impact of incarceration, told the Senate Judiciary Committee in 2012.

Haney continued:

The emptiness and idleness that pervade most solitary confinement units are profound and enveloping. The prison typically provides the prisoners in these units with literally nothing meaningful to do. That emptiness, when combined with the total lack of meaningful social contact, has led some prisoners into a profound level of what might be called “ontological insecurity”—they are not sure that they exist and, if they do, exactly who they are.

For people who spend long stretches in solitary, possible consequences include depression, anxiety and psychosis, and juveniles “are at particular risk” because of where they are in their development, according to the American Academy of Child and Adolescent Psychiatry. It is a brutal reality for any mind, let alone one that is still taking shape. A national survey commissioned by the Justice Department that looked at suicides in juvenile facilities reported in 2004 that half of these people had been confined to their rooms when they took their lives, while 62 percent of them had a history of such confinement.

Yet despite solitary confinement’s dramatic impact on prisoners, we do not actually know how commonly it is used. To be more precise: Nobody knows how many people are in solitary right now, as you are reading these words.

[How many people are killed by police each year? A Post investigation]

According to Solitary Watch, a media and advocacy project, this lack of clarity is partly a result of gaps in how the data is gathered, as there is no thorough national reporting system.

Still, some numbers do exist. The Vera Institute for Justice estimates that more than 80,000 people are isolated in state and federal prisons on any given day — roughly equal to the population of Merced, Calif. But it notes that this number is likely lowballing the real figure because it does not include jails, military facilities, juvenile facilities or immigration detention centers.

Solitary was not a rare experience for young people held in Rikers during Browder’s time there. In 2013, the last year Browder was held in Rikers, there were more than 680 inmates between the ages of 16 and 18 in Rikers on an average day. And on any given day, up to a quarter of them could have been in some form of solitary, according to an investigation into Rikers by the office of Preet Bharara, the U.S. attorney for the Southern District of New York.

Bharara’s sharply critical report, which focused on the years Browder was held there, determined that “a deep-seated culture of violence is pervasive throughout the adolescent facilities at Rikers.” Young inmates told investigators about numerous cases of brutal assaults by corrections officers, and these episodes were not properly reported or investigated, the report found.

Browder told Gonnerman that he attempted suicide multiple times while in isolation. The report from Bharara noted “a number of comments from uniformed staff about inmates using suicide attempts to manipulate the officers and that the attempts therefore did not need to be taken seriously.”

Rikers Island is where most of the inmates in New York City’s jail system are held. It has come under fire for a great many things recently, including the mistreatment of mentally ill inmates, skewed numbers about inmate fights, guards who smuggle contraband and other gaps in security. Last year, undercover investigators were able to smuggle $22,000 worth of drugs and alcohol into Rikers.

New York Mayor Bill de Blasio has announced multiple reforms aimed at improving the situation at Rikers, several of which target problems highlighted by Browder’s situation. De Blasio has announced initiatives to reduce violence at Rikers, end isolation for juvenile inmates and speed up the city’s court system while clearing backlogs of cases.

In January, officials in New York City agreed to stop placing most inmates age 21 and younger in solitary. New York will also curtail how long an inmate can be sentenced to isolation, while inmates with serious mental illnesses or physical disabilities cannot be isolated.

These changes are not occurring in a vacuum, as states across the country have moved recently to change how they approach isolating their most vulnerable inmates. Some other prison systems in the United States have begun to reform and, in some cases, end solitary confinement for mentally ill and young inmates.

Pennsylvania, home to one of the largest prison populations in the country, said this year that it will stop placing inmates with serious mental illnesses in solitary. In 2014, 10 states adopted more than a dozen measures meant to limit the use of solitary, ban it for younger inmates or improve conditions, the Marshall Project reported. Indiana and Ohio limited the amount of time juveniles can be placed in solitary, while Arizona agreed in a legal settlement to let inmates with serious mental health issues spend more time outside their cells.

On Monday, de Blasio offered his condolences to Browder’s family and said many of the reform efforts at Rikers were due to the the story of the teenager held there for three years.

“And a lot of the changes we are making at Rikers Island right now are the result of the example of Kalief Browder,” de Blasio said. “So I wish – I deeply wish we hadn’t lost him, but he did not die in vain.”