Does sleep mediate the association between PTSD symptoms and pain in trauma-affected
2. Project period:
01/02/2020 – 31/01/2021
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
- Professor Poul Jennum, Danish Centre for Sleep Medicine
- Carsten Hjorthøj, Senior Researcher, Copenhagen Research Centre for Mental Health
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
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.
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.
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.
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
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
- 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
- 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
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
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