LAUSR

ABSTRACT Background Insomnia is a global health concern, associated with many mental and physical health conditions. Prevalence of insomnia is reported to increase during adolescence and early adulthood. High levels of insomnia are also reported in adolescents up to 2.5 years after a traumatic event. What is less well understood is the prevalence of insomnia in a trauma exposed population transitioning from adolescence to adulthood. Objective To assess insomnia in the survivors in the 2011 Utøya Island terrorist attack, 2.5 years and 8.5 years after the attack when the majority of survivors were transitioning from late adolescence to early adulthood. Method Participants were 336 survivors of the Utøya Island attack who completed the Utøya Study 2.5 years (T3) and 8.5 years (T4) after the attack. Participants completed a face-to-face interview including the Bergen Insomnia Scale (BIS), which was used to assess insomnia symptoms and prevalence of meeting diagnostic criteria for insomnia. Results Insomnia was indicated in 47.7% of survivors 8.5 years after the attack. Insomnia prevalence did not significantly change from 2.5 to 8.5 years after the attack, though insomnia symptoms (BIS sum score) were found to increase. Age was negatively associated with insomnia at T4, with older age being associated with less insomnia. No significant sex difference was found in insomnia prevalence at T4. Conclusion Almost a decade after the Utøya Island terrorist attack, nearly a half of the young survivors in our study reported insomnia and typical age- and sex-related differences in sleep were not always seen. This rate is almost double what is reported in the general population (20–30%) indicating a high level of unmet need in this population. The implications of such sleep disruption during a critical time for physical, mental, social and cognitive development are far reaching.