More than a quarter of adopted families are in crisis, according to a survey by the BBC and charity Adoption UK.
More than half of those surveyed reported living with a child who was violent, including being punched, kicked or threatened with knives.
More serious incidents included hospital visits and sexual assault.
Despite the challenges, most families said they were glad they adopted. Adoption UK said families needed skilled help and support.
Almost 3,000 subscribers to Adoption UK’s newsletter responded to the survey by BBC Radio 4’s File on 4 programme.
More than a quarter of families, when asked to describe their adoption, said they were facing serious challenges that impacted on the wider family, were at risk of breakdown or disruption, or had already been disrupted.
Almost a half said their adoption was “challenging but stable” and just over a quarter described it as “fulfilling and stable”.
‘We needed help’
Jane knew adopting a little girl from care would not be easy, but nothing prepared her for what came next.
“She was developmentally delayed, so when she was three and a half, all the severe behaviour started to come out”, she said.
“She could be lovely one minute and very violent and aggressive the next.”
Jane, not her real name, and her husband said they asked their local authority for help, but it was not forthcoming.
“The whole time we were saying ‘we’re in trouble, she needs help; we need help.’ But getting anything was a struggle.”
As years went by, their daughter’s behaviour became more extreme. Her husband, Keith, found it difficult to manage.
“She became obsessed with blood,” he said. “She was self-harming and would write on the walls with her own blood. She would pull her own baby teeth out. We reached such a stage that our daughter had become unparentable – she was only six or seven. I couldn’t cope.”
In the end, Keith made the decision to send their daughter back to care. The couple say it was the most difficult decision of their lives.
“She’s in such turmoil, but her behaviour is not her fault,” Jane added.
“She needs help from professionals to make sense of what happened to her. You should be able to get that help.”
The family’s local authority would not comment on their case, but said they were committed to supporting all adoptive families throughout their journey and they “seek to learn lessons” when adoptions do break down.
In the UK, around 5,500 children are adopted every year.
The majority of adoptions involve children over the age of one, siblings and children with disabilities, who have been taken into care.
Many have suffered trauma, neglect and abuse which can result in a range of complex developmental and psychological difficulties. Research suggests almost three quarters of adopted children have significant mental health problems of one kind or another.
Parents who deal with the fallout of these problems, say family life can be extremely difficult.
Many parents described being punched, kicked or threatened with knives. But some reported more serious incidents, including hospital visits and sexual assault.
Dr Sue Armstrong Brown from Adoption UK said it was important not to demonise children.
“We’re talking about trauma-fuelled violence from children who will have witnessed the unthinkable in their early lives,” she said.
“Adoption is not a silver bullet. These children’s problems don’t just disappear overnight. Both adoptive parents and adopted children need skilled help and support.
“Despite the challenges, adopters are resilient and these results reinforce that adoption can work for the vast majority.”
File on 4: Adoption is broadcast on BBC Radio 4 on Tuesday 26th September at 20:00 BST. If you missed it you can catch up on the iPlayer.