Incorporation of prior risk factors including negative childhood events (e.g., childhood maltreatment, parental psychopathology) can aid in building this understanding. Studies indicate that individuals who experience an earlier negative life event may be more sensitized to the effects of a subsequent trauma, and therefore more likely to develop mental health problems. This process has been termed stress sensitization (Van Winkel et al., 2008; Heim and Nemeroff, 2009; Pratchett and Yehuda, 2011). For example, several studies found that childhood maltreatment moderates the association between an adult traumatic event and adult psychopathology, such that those who experienced childhood maltreatment have more severe symptoms after later trauma than those who did not experience maltreatment (Keyes et al., 2014; Pratchett and Yehuda, 2011; Young-Wolff et al., 2012; van Winkel et al., 2013). However, stress sensitization has not been examined in the context of an unanticipated, mass traumatic event such as 9/11. Evidence that negative childhood experiences moderate risk associated with direct and indirect exposure to events such as 9/11 would assist in the identification of individuals at risk of adverse psychological outcomes, and provide further insight into the concept of stress sensitization.
