At least some detainees appeared to be severely psychologically scarred. The report says some detainees were forced to stay awake for over a week at a time. And several detainees suffered from "hallucinations, paranoia, insomnia and attempts at self-harm and self-mutilation." Conditions at the black sites may even have been fatal: In at least one facility, "lack of heat likely contributed to the death of a detainee."

The document provides a circumscribed look at the Senate's investigation. Its 500-odd pages are just the executive summary of a much longer report, estimated to be more than 6,000 pages long. Additionally, some of the information in the executive summary is redacted.

Among its findings are that interrogations of detainees were "brutal and far worse than the CIA represented to policymakers and others." It also suggests that the agency was deceitful in what was gathered from so-called enhanced interrogations, "leaving the false impression the CIA was acquiring unique information from the use of the techniques." The entire management and operation of the detention program was "deeply flawed throughout," the report concludes.

The report details numerous occasions when policymakers were allegedly misled by the CIA. In September 2002, according to the report, the agency did not respond to a series of questions from Sen. Bob Graham, then the chairman of the Senate Select Committee on Intelligence, while "noting in its own internal communications that he would be leaving the committee in January 2003."

President Barack Obama said in a statement that the program detailed in the report was "troubling," though he described the techniques as "enhanced interrogation" instead of torture. "Rather than another reason to refight old arguments, I hope that today's report can help us leave these techniques where they belong — in the past," he said.

Secretary of State John Kerry in a statement described the report as an opportunity to "discuss and debate our history" but then "look again to the future."

"It's important that this period not define the intelligence community in anyone's minds," said Kerry, who lauded the CIA and other intelligence services for risking "their lives to keep us safe and strengthen America's foreign policy and national security."

CIA director John Brennan said in a statement that "the detention and interrogation program had shortcomings and that the agency made mistakes." However, he said the CIA did not mislead the Senate committee and disagreed with the report's conclusion that the CIA's interrogation techniques produced no useful intelligence.

"The intelligence gained from the program was critical to our understanding of Al-Qaeda and continues to inform our counterterrorism efforts to this day," he said.

Former members of the Bush administration rushed to denounce the executive summary before it was released. Speaking to The New York Times, former Vice President Dick Cheney said the expected contents of the report were "a bunch of hooey."

"What I keep hearing out there is they portray this as a rogue operation and the agency was way out of bounds and then they lied about it,” Cheney told the Times. “I think that’s all a bunch of hooey. The program was authorized. The agency did not want to proceed without authorization, and it was also reviewed legally by the Justice Department before they undertook the program."