Young adults who were abused as children share a similar neuroendocrinal trait. When they confront ordinary situations of stress, like taking a test, their brains are flooded with abnormally high levels of the hormone cortisol. According to Queens University psychology professor Karen Harkness:

This kind of reaction is a problem because cortisol kills cells in areas of the brain that control memory and emotion regulation. Over time cortisol levels can build up and increase a person's risk for more severe endocrine impairment and more severe depression.

In her work, Harkness has found that childhood stress can have lasting effects on brain function, exacerbating depression and causing other psychological problems. As cortisol builds up in the brain, it can even cause "blunting" of normal stress responses, leaving young adults completely unable to deal with obstacles most of us would consider tough but surmountable. Her work is just further confirmation of what many neuroscientists have found over the past decade: Psychological horrors don't just haunt our dreams; they change the very structure and function of our brains.