Inresite In Sweden they would be in danger of being diagnosed as a Bortbyting, a replaced person. The concept was based on the fact that people believed in trolls. Trolls was considered a kind of anti humans. They are ugly, greedy, stupid and everything else we do not want to be.
People really believed in trolls. There is even a case when a man was sentenced to death for having sex with a female troll. He confessed and was executed.
Trolls, being in all aspects inferior to humans, were of course jealous on humans for their beautiful children. Occasionally trolls used their abilities to do magic, a magician is still called an artist of trolling because trolla means doing magic, to enter a human house to exchange their troll children for a human child.