"She was older when it started happening, but at the same time, she had years and years of deprivation and limited stimulus," said Jay Reeve, associate professor of psychology at Florida State University and executive vice president of the Apalache Center for Mental Health. "It's exactly as if she was held in captivity in jail."
In Fritzl's case, the trauma may have been more "insidious" because her captor was her father, someone she trusted. In typical cases of captivity and cruelty, victims can direct their fear and anger toward an "anonymous attacker."
"She couldn't unequivocally hate that person because he was her father," said Reeve.
In other abuse cases, victims have other people to turn to for trust, such as a teacher, to mitigate the trauma. "But in her situation she had nothing coming from the environment to help her recover from the effects," he said.
"She had some period of her life when, presumably, she was able to interact with others and be in school and have some social interchange," said Reeve. "But the rape and sexual abuse that she experienced was a pretty stark betrayal of trust."
With the complexity of her trauma, Fritzl most likely has shut down emotionally as a way to cope with the pain and may need myriad therapies and time "to handle her memories and make sense of how why this happened," said Reeve.
Josef Fritzl reportedly hatched the plot to lock up his daughter as a sex slave just after his first sexual assault, when Elisabeth was 11. Seven years later, in 1984, he drugged her with ether, dragged her downstairs and locked her up.
He reportedly handcuffed Elisabeth to a metal pole and kept her in total darkness, returning only to bring her food or to rape her. Often she had to decide whether to have sex or starve.
Police said her mother, Rosemarie Fritzl, said she was completely unaware of the "house of horrors" below. Fritzl reportedly told his wife, who had six other children with her husband, that he was building a nuclear shelter and that Elisabeth had left to join a religious cult.
According to British reports, Elisabeth Fritzl told police she was so afraid of her father that she "submitted herself to him entirely."
Police told the media, "We understand that Elisabeth was his favorite child because she was so pretty."
Jeff Dolgan, senior psychologist at Denver Children's Hospital, said he had never heard of a case this horrific.
"It's beyond creepy," he said. "This takes the cake. Trauma is like throwing a big rock into a pond. The waves go out and we are all sadly traumatized."
Dolgan said Elisabeth Fritzl's mental, physical and emotional wounds will require a network of case managers. "She will need a system of care, not just one person but an adult psychiatrist who will coordinate the rehabilitation. Her world has been this basement. It's like our waking up 500 years from now. This is all she's known."
But doctors see a ray of hope in this demonic scenario. Elisabeth Fritzl may well have been a good caregiver to her children -- Kerstin, Stefan, 18, and Felix, 5 -- and established close bonds with them that will help her heal.
Austrian authorities are trying to get to the bottom of why Josef Fritzl -- a seemingly capable engineer who hid his secret for decades -- could commit such a crime.