title: Time-course of PTSD symptoms in the Australian Defence Force: a retrospective cohort study.
abstract: OBJECTIVE
  Understanding the time-course of post-traumatic stress disorder (PTSD), and the underlying events, may help to identify those most at risk, and anticipate the number of individuals likely to be diagnosed after exposure to traumatic events.
  
  
  METHODS
  Data from two health surveys were combined to create a cohort of 1119 Australian military personnel who deployed to the Middle East between 2000 and 2009. Changes in PTSD Checklist Civilian Version (PCL-C) scores and the reporting of stressful events between the two self-reported surveys were assessed. Logistic regression was used to examine the association between the number of stressful events reported and PTSD symptoms, and assess whether those who reported new stressful events between the two surveys, were also more likely to report older events. We also assessed, using linear regression, whether higher scores on the Kessler Psychological Distress Scale or the Alcohol Use Disorder Identification Test were associated with subsequent increases in the PCL-C in those who had experienced a stressful event, but who initially had few PTSD symptoms.
  
  
  RESULTS
  Overall, the mean PCL-C scores in the two surveys were similar, and 78% of responders stayed in the same PCL-C category. Only a small percentage moved from having few symptoms of PTSD (PCL-C < 30) in Survey 1 to meeting the criteria for PTSD (PCL-C ≥ 50) at Survey 2 (1% of all responders, 16% of those with PCL-C ≥ 50 at Survey 2). Personnel who reported more stressful lifetime events were more likely to score higher on the PCL-C. Only 51% reported the same stressful event on both surveys. People who reported events occurring between the two surveys were more likely to record events from before the first survey which they had not previously mentioned (OR 1.48, 95% CI (1.17, 1.88), p < 0.001), than those who did not. In people who initially had few PTSD symptoms, a higher level of psychological distress, was significantly associated with higher PCL-C scores a few years later.
  
  
  CONCLUSIONS
  The reporting of stressful events varied over time indicating that while the impact of some stressors endure, others may increase or decline in importance. When screening for PTSD, it is important to consider both traumatic experiences on deployment and other stressful life events, as well as other mental health problems among military personnel, even if individuals do not exhibit symptoms of PTSD on an initial assessment.
authors.affiliation: School of Public Health,The University of Queensland,Herston Road,Herston,Qld 4006,Australia.
authors.forename: M
authors.initials: M
authors.lastname: Waller
authors.affiliation: School of Public Health,The University of Queensland,Herston Road,Herston,Qld 4006,Australia.
authors.forename: F J
authors.initials: FJ
authors.lastname: Charlson
authors.affiliation: Institute for Resilient Regions,The University of Southern Queensland,Springfield Central,Qld 4300,Australia.
authors.forename: R E E
authors.initials: RE
authors.lastname: Ireland
authors.affiliation: School of Public Health,The University of Queensland,Herston Road,Herston,Qld 4006,Australia.
authors.forename: H A
authors.initials: HA
authors.lastname: Whiteford
authors.affiliation: School of Public Health,The University of Queensland,Herston Road,Herston,Qld 4006,Australia.
authors.forename: A J
authors.initials: AJ
authors.lastname: Dobson
mesh_terms: D006801:Humans; D008877:Middle East; D008889:Military Personnel / Q000523:psychology*; D012189:Retrospective Studies; D013313:Stress Disorders, Post-Traumatic / Q000175:diagnosis / Q000523:psychology*; D013315:Stress, Psychological
keywords: Delayed onset; PTSD; military; traumatic events