Very stressful events affect the brains of girls and boys in different ways, a Stanford University study suggests.
A part of the brain linked to emotions and empathy, called the insula, was found to be particularly small in girls who had suffered trauma.
But in traumatised boys, the insula was larger than usual.
This could explain why girls are more likely than boys to develop post-traumatic stress disorder (PTSD), the researchers said.
Their findings suggest that boys and girls could display contrasting symptoms after a particularly distressing or frightening event, and should be treated differently as a result.