NEW YORK — Government lawyers and intelligence officials assured themselves of one crucial outcome before the United States permitted a terrifying way of interrogating prisoners.
They knew the methods inflicted on terrorism suspects would be painful, shocking, and beyond what the country had accepted. But none of it, they concluded, would cause long-lasting psychological harm.
Fifteen years later, it is clear they were wrong.
Today in Slovakia, Hussein al-Marfadi describes permanent headaches and disturbed sleep, plagued by memories of dogs inside a blackened jail. In Kazakhstan, Lutfi bin Ali is haunted by nightmares of suffocating at the bottom of a well.
In Libya, the radio from a passing car spurs rage in Majid Mokhtar Sasy al-Maghrebi, reminding him of the CIA prison where ears-splitting music was just one assault to his senses.
Some ex-prisoners say they are no longer themselves. “I am living this kind of depression,” said Younous Chekkouri, a Moroccan who fears going outside because he sees faces of Guantánamo guards in the crowds. “I’m not normal anymore.”
After enduring agonizing treatment in secret CIA prisons around the world or coercive practices at the military detention camp at Guantánamo Bay, Cuba, dozens of detainees developed persistent mental health problems, according to previously undisclosed medical records, government documents, and interviews with former prisoners and military and civilian doctors.
Some emerged with the same symptoms as American prisoners of war who were brutalized decades earlier by some of the world’s cruelest regimes.
Those subjected to the tactics included victims of mistaken identity or of flimsy evidence the United States later disavowed. Others were foot soldiers for the Taliban or Al Qaeda.
Some were hardened terrorists, including those accused of plotting the Sept. 11 attacks or the 2000 bombing of the American destroyer Cole. In several cases, their mental status has complicated the ongoing effort to bring them to justice.
Americans have long debated the legacy of post-Sept. 11 interrogation methods, asking whether they amounted to torture or succeeded in extracting intelligence.
But even as President Obama continues transferring people from Guantánamo and Donald J. Trump, the Republican presidential nominee, promises to bring back techniques, now banned, such as waterboarding, the human toll has gone largely uncalculated.
At least half of the 39 people who went through the CIA’s “enhanced interrogation” program, which included depriving them of sleep, dousing them with ice water, slamming them into walls, and locking them in coffin-like boxes, have since shown psychiatric problems, The New York Times found.
Some have been diagnosed with post-traumatic stress disorder, paranoia, or psychosis.
Hundreds more detainees moved through CIA “black sites” or Guantánamo, where the military inflicted sensory deprivation, menacing with dogs, and other tactics on men who show serious damage. Nearly all have been released.
“There is no question that these tactics were entirely inconsistent with our values as Americans, and their consequences present lasting challenges for us as a country and for the individuals involved,” said Ben Rhodes, the deputy national security adviser.
The United States government has never studied the long-term psychological effects of the interrogation practices. A Defense Department spokeswoman, asked about long-term mental harm, responded that prisoners were treated humanely. A CIA spokesman declined to comment.
Researchers caution that it can be difficult to determine cause and effect with mental illness. Some prisoners had underlying psychological problems that may have made them more susceptible to long-term difficulties; others appeared to have been remarkably resilient.