Does sleep mediate the association between PTSD symptoms and pain in trauma-affected refugees?

​1. Title: 

Does sleep mediate the association between PTSD symptoms and pain in trauma-affected refugees? 

2. Project period: 

01/02/2020 – 31/01/2021 

3. Investigator(s): 

Joakim Friis, Pre-graduate Researcher and Medical Student. 

4. Supervisors and collaborative partners: 

  • Associate Professor Jessica Carlsson, CTP 
  • Hinuga Sandahl, MD, PhD student, CTP 
  • Associate Professor Kristina Bacher Svendsen, Aarhus University, outpatient clinic for sleep disturbances 
  • Professor Poul Jennum, Danish Centre for Sleep Medicine 
  • Carsten Hjorthøj, Senior Researcher, Copenhagen Research Centre for Mental Health 

5. Background 

Sleep disturbance is well recognized in both post-traumatic stress disorder (PTSD) and pain conditions. In PTSD, sleep disturbances represent core diagnostic criteria of the disorder and include nightmares, problems initiating and maintaining sleep, awakenings and consequently reduced length and quality of sleep. Similarly, pain-related conditions and sleeping difficulties frequently co-occur. 

The concept of hyperarousal has been linked to both the pathogenesis of insomnia and to the neurobiological changes in the aftermath of traumatic events and may be a commonality underlying trauma and insomnia(1). Hyperarousal may increase pain sensitivity, pain related anxiety and pain-avoidant behaviours, which can result in chronic pain. Moreover, ongoing sleep disturbances may serve to maintain PTSD and chronic pain over time(1,2). 

Clinical guidelines for treatment of PTSD and affiliated symptomatology including sleep disturbances and chronic pain, derived from research on other populations fail to account for the specific circumstances experienced by refugees, and cannot be assumed to apply to trauma-affected refugees in general (3). 

Recent randomised trials on trauma-affected refugees show that it is a group with high risk of PTSD and cooccurring sleep disturbances and pain and further often hard to treat(4). Therefore, an improved understanding of the relation between sleep disturbances and chronic pain is of value to improve the interventions offered and thus the treatment outcome.

 6. Aim/s 

The aim of this study is to examine if sleep mediates the association between PTSD symptoms and pain in trauma-affected refugees. The following hypothesis will be tested: - Sleep disturbances mediate the associations between PTSD symptoms and pain severity and pain interference in trauma-affected refugees. 

7. Methods

The research project is based on data from a previous randomised controlled trial conducted at CTP in 2016-2019 Treatment of sleep disturbances in trauma-affected refugees – a randomised controlled trial (PTF5)(5). Longitudinal data will be used to investigate possible mediation using path analysis. 

7.1 Number of participants (N) 

219 trauma-affected refugees. 

7.2 Population 

Trauma-affected refugees or family reunited with a refugee fulfilling the criteria for Posttraumatic Stress Disorder and sleep disturbances/Pittsburgh Sleep Quality Index (PSQI) > 8 referred for treatment at CTP. 

7.3 Description of data and data collection 

The participants of this study completed self-administered rating scales as a part of the randomised trial. The below mentioned rating scales will be used in this study. For more information on the remaining rating scales please see trial protocol (5). Data from these ratings will be used in testing our hypothesis. 

  • Sleep: Sleep quality and severity of sleep disturbances are measured on the Pittsburgh Sleep Quality Index (PSQI)(6,7). 
  • Posttraumatic stress disorder: The Harvard Trauma Questionnaire (HTQ) is an internationally applied and thoroughly validated self-administered rating scale assessing the severity of PTSD symptoms. 
  • Pain: Brief Pain Inventory short form (BPI) is a self-administered rating scale assessing severity and interference of pain, impact of pain on daily function, location of pain, pain medications and amount of pain relief in the past 24 hours or the past week. 

7.4 Application/acceptance from the Danish Data Protection Agency, the National Committee on Health Research Ethics 


7.5 Analysis 

Analysis will be conducted to test sleep disturbances (measured on Pittsburgh Sleep Quality Index) as a mediator between PTSD symptom severity (measured on Harvard Trauma Questionnaire) and pain severity and interference (measured on Brief Pain Inventory) controlled for demographic covariates. Mediation occurs if sleep disturbances (mediating variable) explains part of or all of the association between PTSD (independent variable) and pain (dependent variable) in a causal pathway. Mediation will be analysed within a path analysis framework by conducting multiple linear regression (MLR). The statistical analysis will be performed using STATA 16. 

8. Expected results 

The project will be the first to investigate if sleep is a mediator of the association between PTSD and pain in trauma-affected refugees and will thus contribute with new knowledge. If sleep is a mediator as hypothesised, successful treatment of sleep disturbances should yield change in symptoms of pain. 

9. Dissemination of results

The study results will be disseminated in several contexts, at least one paper will be submitted to a peerreviewed journal and the results will be presented as poster and oral presentations at several scientific and public conferences. 

10. References 

1. Sinha SS. Trauma-induced insomnia: A novel model for trauma and sleep research. Sleep Med Rev [Internet]. 2015/07/05. 2016;25:74–83. Available from: 

2. Noel M, Vinall J, Tomfohr-Madsen L, Holley AL, Wilson AC, Palermo TM. Sleep Mediates the Association Between PTSD Symptoms and Chronic Pain in Youth. J Pain [Internet]. 2018;19(1):67–75. Available from: 

3. Crumlish N, O’Rourke K. A systematic review of treatments for post-traumatic stress disorder among refugees and asylum-seekers. J Nerv Ment Dis [Internet]. 2010;198(4):237–51. Available from: 

4. Sonne C, Carlsson J, Bech P, Elklit A, Mortensen EL. Treatment of trauma-affected refugees with venlafaxine versus sertraline combined with psychotherapy - a randomised study. BMC Psychiatry [Internet]. 2016/11/09. 2016;16(1):383. Available from: 

5. Sandahl H, Jennum P, Baandrup L, Poschmann IS, Carlsson J. Treatment of sleep disturbances in trauma-affected refugees: Study protocol for a randomised controlled trial. Trials [Internet]. 2017/11/08. 2017;18(1):520. Available from: 

6. Buysse DJ, Reynolds Iii CF, Monk TH, Berman SR, Kupfer DJ. The Pittsburgh sleep quality index: A new instrument for psychiatric practice and research. Psychiatry Res [Internet]. 1989;28(2):193–213. Available from: 

7. Insana SP, Hall M, Buysse DJ, Germain A. Validation of the Pittsburgh Sleep Quality Index Addendum for Posttraumatic Stress Disorder (PSQI-A) in U.S. Male Military Veterans. J Trauma Stress [Internet]. 2013;26(2):192–200. Available from:

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