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Abstract Introduction Evening-type and insomnia symptoms are closely related to each other and independently associated with depressive symptoms, yet few studies have examined the potential interaction between these two conditions. Therefore, we aimed to examine the associations of evening-type and insomnia symptoms with depressive symptoms among Chinese young people, with a specific focus on the joint effects of the two conditions on depressive symptoms. Methods Participants aged between 12 to 25 were invited to participate in an online survey from December 15, 2022, to May 26, 2023. The reduced Morningness and Eveningness Questionnaire, Insomnia Severity Index, and Patient Health Questionnaire-9 were used to evaluate chronotypes, insomnia and depressive symptoms, respectively. Multivariate logistic regression models were used to examine the independent associations of chronotypes and insomnia symptoms with depressive symptoms, while additive interaction models were used to further explore the joint effects of chronotypes and insomnia symptoms on depressive symptoms. Results Of the 6145 eligible participants, the prevalence of evening-type and insomnia symptoms were 24.9% and 29.6%, respectively. Both evening-type (adjusted odds ratio AdjOR: 3.62, 95% CI: 3.19-4.11) and insomnia symptoms (AdjOR: 11.75, 95% CI: 10.26-13.47) were associated with an increased risk of depressive symptoms. In addition, the additive interaction models showed that there is an enhanced risk of depression related to interaction between evening-type and insomnia symptoms (relative excess risk of interaction RERI: 12.39, 95% CI: 3.62-21.17). In the subgroup analyses for adolescents (RERI: 10.37, 95% CI: 5.44-15.30) and young adults (RERI: 15.48, 95% CI: 5.49-25.46), positive interactions between evening-type and insomnia symptoms on depressive symptoms remained. Conclusion The present study provided additional evidence demonstrating the independent and joint contributions of evening-type and insomnia symptoms to depressive symptoms among young people. In particular, there is an interaction effect of evening-type and insomnia symptoms, further increasing the risk of depressive symptoms. Our findings argue the need for addressing both sleep and circadian factors in the management of depressive symptoms in young people. Support (if any) This study was supported by grants from Fujian Provincial Health technology project (No. 2022GGB015 and 2022CXB019) and Natural Science Foundation of Xiamen City (No. 3502Z20227148).
Que et al. (Sat,) studied this question.