Predictors of early adulthood insomnia following exposure to a single mass violence attack during adolescence: 7-13 year follow-up from the Utøya and HUNT studies.

Background: The long-term impact of mass violence attacks is practically unknown, especially in children and adolescents. In a previous study, we found that 8.5 years after a terror attack targeting mainly adolescents, nearly half of the survivors met diagnostic criteria for insomnia. Objectives: The aims of this study were to investigate: (1) whether exposure to a single mass violence event during adolescence increases the risk of insomnia almost a decade later above that expected for a non-exposed population; and (2) whether prior interpersonal violence exposure and early post-traumatic reactions predict later insomnia. Method: Participants were survivors of the 2011 Utøya Island terrorist attack ( n  = 279) and controls from the HUNT Norwegian general population study ( n  = 35,664). Early adulthood insomnia was assessed using four items from the Karolinska Sleep Questionnaire 8.5 years after the attack. Participants who had also completed earlier data collection waves for both studies ( n  = 116 and 2382, respectively) were included in logistic regression models testing the associations between predictors during adolescence and later insomnia. Results: Nearly a decade after the Utøya attack, 38.4% ( n  = 56) of the survivors reported symptoms of insomnia indicative of probable insomnia compared to 20.5% ( n  = 5771) of controls. Terror exposure during adolescence was a significant predictor of later insomnia [odds ratio (OR) = 3.18, 95% confidence interval (CI) = 2.05-4.87, p  < .001]. Early post-trauma symptoms of anxiety and depression (OR = 1.34, 95% CI = 1.02-1.76, p  = .033) and weekly headaches (OR = 1.64, 95% CI = 1.08-2.47, p  = .018) were also significant predictors while controlling for background factors and other predictors. Conclusion: Long-term assessment and treatment are needed for survivors of mass violence to improve resilience and recovery.