Traumatic events and PTSD symptoms

Exposure to various types of potentially traumatic events was assessed using a measure derived from combining the trauma event list of the Harvard Trauma Questionnaire [23], and the first part of the Posttraumatic Diagnostic Scale (PDS; [26]), resulting in a total of 23 items. Participants indicate if a given potentially traumatic event was experienced and/or witnessed. Subsequently, participants’ overall trauma exposure is established by summing up the number of types of trauma they had been exposed to. The severity of 17 PTSD symptoms according to the Diagnostic and Statistical Manual of Mental Disorders 4th edition (DSM-IV; [24]) criteria was assessed using the PDS [25, 26]. The frequency of each symptom in the last month was rated on a 4-point scale ranging from 0 = “never” up to 3 = “5 times per week or more/nearly always”), yielding a total severity score ranging from 0 to 51. Besides the assessment of symptom levels, the PDS allows making a categorical probable diagnosis of PTSD according to DSM-IV criteria, which requires at least one symptom of re-experiencing, three of avoidance, and two of hyperarousal. The PDS has demonstrated good psychometric properties [26]. The internal consistency in the current sample was α = .96.

To take into account the changes of PTSD in the DSM 5 the symptoms of PTSD in this sample were subdivided into four factors according to King and colleagues emotional numbing model of PTSD [27]. The model was first tested in treatment-seeking male veterans resulting in four correlated factors of Re-experiencing, Avoidance, Numbing, and Hyperarousal and was confirmed in other trauma-related populations, such as refugees [28].