Sleep restriction is associated with a decrease in positive affect in individuals with a history of mild traumatic brain injury
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- Institutt for psykologi 
Individuals sustaining a mild traumatic brain injury (mTBI) are at risk of developing sleep problems and affective dysfunction postinjury. Sleep is critically involved in affective functioning, thus individuals exposed to the double hazard of mTBI and sleep loss might be at particular risk of developing affective dysfunction. If psychological resilience protects individuals from the impact of postinjury sleep loss, it may play a vital role in both treatment and prevention of mTBI complications. The present study is the first study to experimentally examine the links between sleep, affective functioning, and resilience in individuals with a history of mTBI. Eighteen adults (nine with mTBI, nine community controls), aged 19-60, completed a two-week sleep manipulation protocol of 10 nights of habitual baseline sleep, followed by three nights of sleep restriction (two hours less than mean baseline sleep duration). Participants’ sleep was monitored at home with sleep diary and actigraphy recordings. Participants completed questionnaires of affective state at five sessions (three baseline measurements, two under the sleep restriction condition). Psychological resilience was measured before inclusion to the present study using the “Resilience Scale for Adults”. All participants completed all procedures. Repeated measures and mixed design ANOVAs and ANCOVAs were conducted to compare affective state levels between habitual sleep and sleep restriction conditions, and to investigate the influence of psychological resilience. Sleep restriction led to a significant decrease in positive affect in individuals with a history of mTBI, but not in the control group. Psychological resilience substantially moderated the impact of sleep restriction. When accounting for potential differences in resilience levels between individuals with a history of mTBI and the control subjects, the mTBI group was still more vulnerable to the impact of sleep restriction. Thus, the results support a “double hazard effect” of mTBI-history and sleep loss.