Objective: The purpose of this study was to examine whether there is a bidirectional relationship between, on one hand, anxiety and depression and, on the other hand, insomnia over the course of a year.
Methods: A randomly selected sample of 3000 participants from the general population filled out a baseline survey (N=1812) and a 1-year follow-up survey (N=1498) on anxiety, depression, and insomnia.
Results: On cross-sectional analyses, bivariate correlations showed that anxiety, depression, and insomnia were significantly intercorrelated (varphi=.31-.54). On prospective analyses, logistic regression analyses demonstrated that anxiety at baseline [odds ratio (OR)=4.27 (8% of variance)] and depression at baseline [OR=2.28 (2% of variance)] were related to new cases of insomnia on follow-up. Furthermore, insomnia at baseline was related to new episodes of high anxiety and high depression on follow-up [OR=2.30 (2% of variance) and OR=3.51 (4% of variance), respectively].
Conclusion: Evidence suggests that there is a bidirectional relationship between, on one hand, anxiety and depression and, on the other hand, insomnia. This suggests that anxiety, depression, and insomnia are intertwined over time, implying implications for theoretical conceptualizations and interventions.