Sky News has already reported on the case of Bethany, a teenager with autism who is left locked up in segregation for 24 hours a day.
Her father Jeremy said his daughter was treated like a "vicious dog".
Now, we talk to another teenager with autism who spent 14 months in two mental health units, and who says that being pinned down by staff made her feel like a caged animal.
Holly Williams first started experiencing problems with her mental health when she 15.
She was suffering from anxiety and depression, and did not qualify for support in the community.
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That being the case, her family decided she should seek help in an assessment and treatment unit.
It was a decision they and Holly would come to regret.
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"They were quite rough – they would grab me," she said.
"Either on the mattress or on the floor, a hard floor. You'd have one person on one leg, another person on the other leg. One person on your arm, another on the other arm and one person on your head."
Holly would be forcibly restrained in this way every time she showed any signs of heightened anxiety.
But it actually made her feel even more anxious.
Because of her autism she does not like to be touched.
Once, Holly said she was pinned to the floor like this for several hours.
"Some people don't like being touched," she said. "Also it doesn't really help you to learn to cope. They are not teaching you any coping strategies, or therapies."
She added: "You're just having someone physically stop you until you're calm and then leave you. There's no support in that, no support after it, no support before your incident. You're just left alone to have an incident. You're restrained and left alone again until the next time."
Holly says the staff in her unit were not autism-trained and did not understand her condition.
There were 70 of these incidents when she was forcibly restrained. She says staff would not try any other method of calming her down.
The forcible restraint, almost always involving five adults pinning her to the ground, was the only method of control that was used, she said.
Holly spent 14 months in two different units. She was admitted voluntarily at the beginning, but was later sectioned under the Mental Health Act and not allowed to leave.
"I was really distressed," she said. "I just wanted to go home. But they wouldn't let me leave or go outside – not even in the garden, so I became more anxious.
"I started pulling the curtains down. They put me in a five-person restraint for five hours on the floor.
"Nobody explained why they were doing this to me. They were doing this to other patients all the time, every day."
Her mother Emma Clark says she was "heartbroken and powerless" as she saw her daughter's condition deteriorate rapidly during this time.
She said Holly was over-medicated and this led to rapid weight gain – almost "three stones in three months".
That in turn led to further "body image anxiety".
Emma said: "Nobody wants somebody to lay hands on your kid.
"You think, if I was there, I'd stop them because she was only being herself. It makes you feel like they are bullies.
"If we could have wrapped her up and brought her home we would have done. But we were told if we took her out of the unit without permission she would be sectioned. It's just heartbreaking. It's like a knife in your heart, you have a tightness across your chest at all times."
