In a lot of books/movies you see this scene, the latest example that I found was in "when we were orphans" book:
A perfectly normal, healthy woman is kidnapped. After 20 years of abuse, physical and psychological (sort of a slave) she is found by some carers and admitted to a retirement home. Her son finally finds her, but although she can speak normally, answer questions, she fails to recognise him and doesn't react in any way at the news that she's her son.
I am wondering what does it mean from a clinical point of view when a person "loses his mind" like this and if it actually can happen or is just a myth. I'm not talking here about dementia or other diseases like that, but about diseases that get triggered by abuse.