One group, of 14 girls and 16 boys, had suffered at least one episode of severe stress or trauma while a second group, of 15 girls and 14 boys, had not been exposed to any.
In the group of traumatised boys and girls, there was evidence that one area of the insula - the anterior circular sulcus - had changed in size and volume compared with the group with no trauma.
This shows that the insula is changed by exposure to acute or long-term stress and plays a key role in the development of PTSD, the researchers said.