RIVERSIDE, Calif. -- They are safe for now and, according to authorities, they are relieved.

But the 13 children, aged 2 to 29, rescued from what was described as nothing less than a torture chamber will have years of therapy ahead, experts say, as they learn to live in a world that, until a week ago, they never really knew.

Since arresting David and Louise Turpin earlier this week, authorities said they have learned the children were confined to the house, chained to furniture, starved and often deprived the use of a toilet. Some of the children were so detached they didn't understand the concept of a police officer or medicine.

"You don't need to learn what a police officer is from going to school, you learn that from just being out in the world," said Patricia Costales, chief executive of The Guidance Center, a Long Beach, California-based non-profit that provides mental health therapy to thousands of children.

"To not even know something like that really speaks to how incredibly controlled their environment was. They're going to experience a culture shock even apart from the trauma they have undergone," said Costales, a licensed clinical social worker and therapist who has treated kidnap victims, some held for years.

The Turpin siblings, seven adults and six children, likely need years of therapy, psychological experts said, adding that if possible it would be best to keep them together.

The youngest should have the easiest road to recovery, Costales said, but added she is optimistic that over time all could eventually learn to lead relatively normal lives.

"Their brains are still adapting, they're still forming, they're still developing their understanding of the world," she said of the younger children. "But someone who has experienced these things for 20-some years of their life will have a lot of learning to do about what relationships are like, what the world is like, how they're supposed to be treated."

Even being separated from their parents, who are now in jail on torture, child abuse and other charges, could be unsettling initially to some of the children, said Jessica Borelli, a clinical psychologist and professor of psychology and social behaviour at University of California, Irvine.

"When we come into this world, our attachment figures are our primary sources of safety and security, no matter how abusive they are," she said. "That impulse or that draw to be back with the people who are supposed to keep you safe is incredibly strong, and that is what has to be overridden to get out of an abusive situation."

Police were summoned to the Turpin home in Perris, a city of about 70,000 people 60 miles southeast of Los Angeles, on Sunday after the couple's 17-year-old daughter jumped out of a window and called 911. She had planned the escape for two years and fled with a sibling who became too scared and turned back, Riverside County authorities said.

The fact that she carried out such a courageous act, Borelli said, shows she could play a leadership role in helping her siblings recover.

"To me, that is a sign she has something inside of her that is really healthy," she said. "One of the things that happens with really prolonged abuse like this is the instincts about self-protection and the desire to protect oneself are totally disrupted -- but she has it. So, I think she might be someone who can help."

When deputies arrived at the home they found a 22-year-old chained to a bed. The house reeked of human waste and evidence of starvation was obvious, with the oldest sibling, a 29-year-old woman, weighing only 82 pounds, said Riverside County District Attorney Mike Hestrin.

The children were tethered to beds with chains and padlocks as punishment and allowed to do little but write in journals, authorities said.

David Turpin, 56, and Louise Turpin, 49, have pleaded not guilty to multiple counts of torture, child abuse, dependent adult abuse and false imprisonment dating to 2010, when the family moved to California from outside Fort Worth, Texas. David Turpin also pleaded not guilty to performing a lewd act on a child under age 14.

Each is held on $12 million bail.

David Turpin had worked as an engineer for both Lockheed Martin and Northrop Grumman. Louise Turpin identified herself as a housewife in a 2011 bankruptcy filing.

The family led a nocturnal existence and slept all day, which kept them largely out of sight from neighbours in their tight-knit suburban-styled community.

Authorities have given no motive for the parents' behaviour, which Hestrin called "depraved."

Abbey Kanzer, a clinical psychologist at the Center for Victims of Torture in St. Paul, Minnesota, said recovery can take years but there is hope in even the most horrific cases.

"The hope for treatment is to find a way so the trauma becomes a contained part of what happened to them," she said. "It becomes part of their story, but not their complete story."

Melley reported from Los Angeles. Associated Press writers Michael Virtanen in Pittsburgh and Michael Balsamo, John Antczak, Andrew Dalton and Christopher Weber in Los Angeles contributed to this report.