Mind at rest, mind at risk: A prospective population-based study of sleep and subsequent mental disorders.

Background: Depression and anxiety disorders are highly prevalent among young adults, with evidence suggesting sleep problems as key risk factors. Objective: This study aimed to examine the association between insomnia and sleep characteristics with major depressive episode (MDE) and anxiety disorders, and the association after accounting for baseline mental health symptoms. Methods: We conducted a prospective cohort study using data from the Students' Health and Wellbeing Study (SHoT), surveying Norwegian higher education students aged 18 to 35 (N = 53,362). A diagnostic assessment of 10,460 participants was conducted in 2023. Self-reported insomnia, sleep duration, sleep onset latency, and wake after sleep onset were recorded in 2022. MDE and five types of anxiety disorders were assessed after one year using a self-administered CIDI 5.0. Analyses adjusted for age, sex, baseline mental health symptoms, and somatic conditions. Results: Insomnia in young adults was associated with a significantly increased risk of MDE (adjusted RR = 3.50, 95 % CI = 3.18-3.84) and generalized anxiety disorder (GAD) (adjusted RR = 2.82, 95 % CI = 2.55-3.12) one year later. Sleep duration showed a reversed J-shaped association with mental disorders, with both short and, to a lesser extent, long sleep durations linked to elevated risks, even after adjusting for baseline mental health symptoms and somatic conditions. Although the associations were attenuated after adjustment, they remained statistically significant. Conclusion: Sleep disturbances, including insomnia and abnormal sleep durations, predict mental health issues in young adults, even after accounting for baseline mental health and somatic health. Addressing sleep problems early may help prevent subsequent mental health conditions in this population.