Two people can survive the same terrifying event, yet only one may later develop post-traumatic stress disorder. Why? PTSD is not determined simply by how frightening an experience was, but by a complicated interaction among biology, previous experiences, the nature of the trauma, psychological responses, and what happens afterward. Research suggests that genetics, brain circuitry, perceived helplessness, social support, and prior trauma can all influence whether the nervous system successfully returns to baseline. Understanding these differences helps explain why trauma exposure and PTSD are not the same thing. In this episode, we examine why some brains recover while others remain trapped in survival mode.