Sarah is living proof that "life after hell" is possible.

For more than 20 years she says she endured beatings, rape and degradation at the hands of her family.

She tells of being locked in sheds, made to eat from a dog's bowl and left tied to a tree naked and alone in the bush.

Her abusers spanned three generations and included her grandfather, father and some of her brothers. She has scars across her body.

"This is from a whipper snipper," she says, pointing to a deep gouge of scar tissue wrapped around the back of her ankle. Higher up is another she says was caused by her father's axe.

But Sarah survived.

Now she is speaking out in the hope of empowering others trapped in abusive situations.

"There is life after hell, but you need to learn how to believe in yourself," she says.

A reality for many Australian adults

As confronting as Sarah's case may be, she is not alone.

While most people assume child abuse ends at adulthood, it can bring control, fear and manipulation that can last a lifetime.

Incestuous abuse into adulthood affects roughly 1 in 700 Australians, according to research by psychiatrist Warwick Middleton — one of the world's leading experts in trauma and dissociation. If that estimate is accurate, tens of thousands of Australian adults like Sarah are being abused by family members into their 20s or even up to their 50s.

Warwick Middleton is one of the world's leading experts in trauma and dissociation. ( ABC News: Tracey Shelton )

"It's a mechanism of ongoing conditioning that utilises every human's innate attachment dynamics, and where fear and shame are used prominently to ensure silence — particularly shame," says Professor Middleton, an academic at the University of Queensland and a former president of the International Society for the Study of Trauma & Dissociation.

He has personally identified almost 50 cases among his patients, yet there was no literature or studies on this kind of abuse when he began publishing his findings.

Hidden in 'happy' families, successful careers

Sydney criminologist Michael Salter has found similar patterns in his own research. He said cases of incest are "fairly likely" to continue into adulthood, but this extreme form of domestic abuse is unrecognised within our health and legal systems.

"It's unlikely that these men are going to respect the age of consent," says Mr Salter, who is an associate professor of criminology at Western Sydney University. "It doesn't make sense that they would be saying, 'Oh you're 18 now so I'm not going to abuse you anymore'. We're just not having a sensible conversation about it."

The ABC spoke with 16 men and women who described being abused from childhood into adulthood.

They said their abusers included fathers, step-fathers, mothers, grandparents, siblings and uncles.

Medical and police reports, threatening messages and photos of the abuse supported these accounts. Some family members also confirmed their stories.

Sarah says her father and his friends photographed some of her abuse. One image shows her beaten and bloodied with a broken sternum at five. In another photo (pictured here), she cowers as her father approaches with a clenched fist.

Most victims described their families as "well-respected" and outwardly "normal-looking", yet for many the abuse continued well after their marriage and the birth of their own children, as they navigated successful careers.

"You see a lot of upper-income women who are medical practitioners, barristers, physiatrists — high functioning in their day-to-day lives — being horrifically abused on the weekends by their family," Mr Salter says.

Helen, a highly successful medical professional, says she hid sexual abuse by her father for decades.

"They didn't see the struggle within," she says.

A mental 'escape'

Professor Middleton describes abuse by a parent as "soul destroying". In order to survive psychologically, a child will often dissociate from the abuse.

Compartmentalising memories and feelings can be an effective coping strategy for a child dependent on their abuser, says Pam Stavropoulos, head of research at the Blue Knot Foundation, a national organisation that works with the adult survivors of childhood trauma.

The extreme and long-lasting nature of ongoing abuse can result in dissociative identity disorder, which on the one hand can shield a victim from being fully aware of the extent of the abuse but can also leave them powerless to break away, Ms Stavropoulos says.

Claire*, 33, describes her dissociation as both her greatest ally and her worst enemy.

"You feel like you've keep it so secret that you've fooled the world and you've fooled yourself," she says.

In her family, women — her mother and grandmother — have been the primary physical and sexual abusers and she says some of her abuse is ongoing.

"In a way you have freedom, but at the same time you are trapped in a nightmare," she says.

'It's like he's melted into my flesh'

For many, the attachment to an abuser can be so strong, they lose their own sense of identity.

Kitty, who was abused by her father for more than five decades until his recent death, says she did everything her family said to try to win their love.

"I thought I was some kind of monster because I still love my father," she says. "It's like he's melted into my flesh. I can feel him. He is always here."

Mr Salter says the conditioning is difficult to undo, and often leaves a victim vulnerable to "opportunistic abuse" and violent relationships.

"If the primary deep emotional bond that you forge is in the context of pain and fear then that is how you know that you matter," he says. "It's how you know that you are being seen by someone."

Many of those the ABC spoke with were also abused by neighbours or within the church or school system. Others married violent men.

"They don't have the boundaries that people normally develop," Mr Salter says, adding that parental abuse could leave them "completely blind to obvious dodgy behaviour because that's what's normal for them".

'You believe they own your body'

Professor Middleton said premature exposure to sex confuses the mind and the body and leaves a child vulnerable to involuntary sexual responses that perpetrators will frequently manipulate to fuel a sense of shame, convincing them they "want" or "enjoy" the abuse.

For Emma*, violent sexual assaults and beatings at home began when she was five and are continuing more than 40 years later.

"When you are naked, beaten, humiliated and showing physical signs of arousal, it really messes with your head. It messes with your sexuality," she says.

"Your sense of what is OK and what isn't becomes really confused. You come to believe that they literally own you and own your body. That you don't deserve better than this."

A medical report viewed by ABC shows Emma required a blood transfusion last month after sustaining significant internal tissue damage from a sharp object. The report stated Emma had a history of "multiple similar assaults".

She said medical staff do want you to get help and sometimes offered to call police.

"What they don't understand is that for me police are not necessarily a safe option," she says.

As a teenager she had tried to report to the police, but was sent back home to face the consequences.

She said a "lack of understanding about the dynamics of abuse and the effects of trauma" mean victims rarely get the response and help they need.

While Emma has been unable to escape the abuse, she has made many sacrifices to shelter her children from it. But they still suffer emotionally, she says.

"It makes it hard for anyone who cares about you having to watch you hurt over and over again."

Incest after marriage and kids

For Graham, it was devastating to find out his wife Cheryl* was being sexually abused by both her parents 10 years into their marriage.

"I had no idea it was going on," he says, of the abuse that continued even after the birth of their children. "The fight between wanting to kill [her father] and knowing it's wrong wasn't fun. I don't think people know what stress is unless they've been faced with something like that."

With Graham's support, the family cut contact with his in-laws. He says the fallout of this abuse ripples through society impacting everyone around both the abused and the abuser.

Mr Salter urges anyone suffering abuse to reach out for help, and for those around them to be supportive and non-judgemental.

"You can get out — don't take no for an answer. Keep fighting until you find someone who is going to help you keep fighting," he says.

A new life

Sarah met Professor Middleton after a suicide attempt at 14, but it took many years for her to trust and accept that things could change.

"I just couldn't grasp I was free. It didn't matter what anyone did," she says.

"I still felt overall that my family was in control of me and at any moment they could kill me."

Through therapy with Professor Middleton — who she spoke of as the only father figure she has ever known — and the support of her friends and partner, Sarah finally broke away from her abusive family to start a new life of her own.

"You need people to help you through it. In the same way that it took other people to cause you the pain, it takes new people to replace them and help you give yourself another go," she says.

"If I can give hope to one other person out there, then all my years of pain will not have been for nothing."

*name changed to protect identity