Copeland et al1 found that more than two-thirds of children in western North Carolina are victims of trauma before their 16th birthday. Yet less than 0.5% developed posttraumatic stress disorder (PTSD).
The striking discrepancy between the prevalence of trauma and the prevalence of PTSD is partly explained by conceptual bracket creep in the definition of trauma. The broader the concept of trauma, the lower the rate of PTSD is likely to be. Indeed, no longer need one be directly exposed to a potentially fatal event to qualify as a victim of trauma. People who merely learn about the serious misfortunes of others now qualify as trauma survivors themselves. As Copeland et al observed, such indirect experiences account for many cases of exposure in their study.
McNally RJ. Trauma in Childhood. Arch Gen Psychiatry. 2007;64(12):1451. doi:10.1001/archpsyc.64.12.1451-a