Tired of pain or so tired it hurts? Mechanisms and factors influencing the temporal relationship between insomnia and pain in adolescents

Sammanfattning: Onset of both chronic pain and insomnia is high during adolescence, a phenomenon believed to be caused by a range of biological, psychological and social factors that are unique or particularly salient during adolescence. Negative mood has been established as a salient mechanism explaining the sleep-pain relationship, but an elaborate understanding of if and how mood mediate the relationship in adolescents is lacking. The current thesis aimed to fill this gap in the literature through three empirical studies that each focused on distinct aspects of the sleep-pain relationship in adolescents. All three studies were based on a prospective dataset, consisting of 2766 adolescents followed across 5 consecutivey early measurement waves.Study I focused on how insomnia and pain longitudinally co-develop during adolescence, finding that they follow each other to a high degree among all adolescents. A late sleep phase and cognitive-emotional presleep arousal predicted steeper rate of change in insomnia and pain. Study II found a bidirectional relationship between insomnia and pain, with the effect of insomnia on pain being significantly stronger than vice versa. Depressed and anxious mood mediated the effect of insomnia on pain, but not vice versa. Study III assessed if the effect of insomnia on pain was mediated by rumination and depressed mood, and if the effect differed between girls and boys. The effect of insomnia on pain was considerably stronger in adolescent girls, compared to boys, and rumination only mediated the effect in girls, while primarily depressed mood mediated the effect in boys.Taken together, these findings have both conceptual and applied implications: the findings add to – and deepen – the understanding of how the relationship between insomnia and pain functions in adolescents. The mechanisms that were identified as mediators, as well as insomnia itself, are also highly modifiable through psychological interventions. Therefore, the findings may inform treatment strategies for adolescents with comorbid insomnia and chronic pain, as well as preventive programs for adolescents at risk for developing insomnia and/or pain.