A doctor treating freed Hamas hostages in Israel says survivors are suffering from an unprecedented level of "extremely severe psychological abuse" endured during captivity. 

"I can tell you that on behalf of all the medical and psychological teams treating those who return, the mental states we encountered have no precedent in medical literature. We feel that we have to rewrite the textbooks of post-trauma," Dr. Renana Eitan told "Sunday Night in America."

Eitan revealed the Tel Aviv Medical Center is actively treating more than 15 former hostages and described their "severe physical and mental abuse."

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"Those held captive were subject to starvation, to beating, to sexual abuse. They were being held in inhumane sanitary conditions. Extremely severe psychological abuse was inflicted on them, including separation from family members, separation of siblings, separation of children from their mothers. They were held in solitary confinement and spent long days in total darkness until they developed severe hallucinations," Eitan claimed. "Children were forced to watch brutal videos. They were under constant threats by weapons and threats to harm them even after they were released. They refer to the forced use of psychiatric drugs and other substances."

Eitan also detailed cases where individuals, though appearing physically unharmed, are dealing with "severe post-traumatic symptoms."

"Some of the home comers, they look happy, they look fine, they look physically fine, and we try to hold on to those optimistic signs, but still, even those who seem fine, we know that most of them [are] suffering from severe post-traumatic symptoms, they have painful, traumatic memories. And they are entering into dissociative states, where for a moment they feel as if they are still in captivity and only later do they return to the understanding that they have been released," she said.

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This week marks two months since the Hamas terror attack on Israel which left 1,200 dead and 240 held hostage. According to the Israeli Ministry of Health, 73 Israelis and 24 foreign citizens have been released from Hamas to date.

Eitan urged the release of the remaining hostages "as soon as possible" as they face a long road ahead of physical and mental rehabilitation.

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FOX News' Greg Palkot contributed to this report.