Objective: We investigated the longitudinal impacts of insomnia on the subsequent developments of anxiety and depression during a four-year follow-up. We further categorized individuals with insomnia into different insomnia subgroups to examine whether the risk of anxiety and depression varies by subtype.
Methods: Participants were identified from National Health Insurance enrollees in Taiwan during 2002-2009. The study included 19,273 subjects with insomnia and 38,546 matched subjects without insomnia. All subjects did not have previous diagnosis of insomnia, sleep apnea, anxiety, or depression.
Results: Compared with non-insomniacs, insomniacs had a higher risk of developing anxiety only [adjusted hazard ratio (HR) = 8.83, 95% CI = 7.59-10.27], depression only (adjusted HR = 8.48, 95% CI = 6.92-10.39), and both anxiety and depression (adjusted HR = 17.98, 95% CI = 12.65-25.56). When breaking down the insomnia subgroups, individuals with a relapse of insomnia (adjusted HR = 10.42-26.80) had the highest risk of anxiety only, depression only, and both anxiety and depression, followed by persistent insomnia (adjusted HR = 9.82-18.98), then remitted insomnia (adjusted HR = 4.50-8.27). All three insomnia subgroups had a greater four-year cumulative incidence rate than the non-insomnia group for anxiety only, depression only, and both anxiety and depression (p < 0.0001).
Conclusion: Our findings reinforce the clinical predictor role of insomnia in the future onset of anxiety or/and depression. Awareness of insomnia and treatment of insomnia should be recommended at clinics, and patterns of insomnia should be monitored to help treatment and control of subsequent psychiatric disorders. Future research with comprehensive data collection is needed to identify factors that contribute to different insomnia subtypes.
Keywords: Anxiety; Depression; Insomnia; Longitudinal; Subtype.
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