Does sleep quality mediate the association between post-traumatic stress disorder symptom severity and pain interference in trauma-affected refugees?

Poor sleep quality is well recognised in both post-traumatic stress disorder (PTSD) and pain conditions. Comorbid chronic pain is prevalent in populations with PTSD and is believed to maintain symptoms of PTSD and increase the complexity of the condition. Ongoing diminished sleep quality may serve to maintain pain and PTSD symptoms, and thus affect the efficacy of first-line PTSD treatment. This study examined the mechanisms underlying the PTSD-pain relationship over time by investigating if perceived sleep quality mediates the relationship between PTSD symptom severity and levels of pain interference. Furthermore, we considered whether the interrelation between these three variables could in fact be linked in an alternative model where the causality was reversed, with pain interference mediating the relation between PTSD severity and perceived sleep quality. Relationships among our variables were assessed within a path analysis framework, conducted and controlled for covariates using structural equation modelling and mediation analysis. The analysis of our hypothesised model revealed that improvement in perceived sleep quality was a significant partial mediator of the association between reduction in PTSD severity and pain interference. Approximately 28% of the effect of PTSD severity on pain interference was mediated by improvement in perceived sleep quality. Evaluation of our alternative model revealed a non-significant mediation effect. Sleep thus represents a modifiable mechanism that contributes to the mutual maintenance of PTSD and pain. The study is the first to investigate these relationships in trauma-affected refugees and thus contributes new knowledge and clinical implications for the treatment of poor sleep quality and pain symptomatology in trauma-affected refugees.