Understanding the Link Between Eveningness and Depression: A Serial Mediation Study of Daytime Sleepiness and Pre-Sleep Arousal

The evening chronotype is consistently associated with depressive symptoms, but the underlying mechanisms remain unclear. This study examined whether daytime sleepiness and pre-sleep arousal mediate the relationship between eveningness and depressive symptoms in adults. In this cross-sectional study, 524 adults were recruited from community health centers in Indonesia using convenience sampling. Chronotype, daytime sleepiness, pre-sleep arousal, and depressive symptoms were assessed using the Morningness-Eveningness Questionnaire (MEQ), Epworth Sleepiness Scale (ESS), Pre-Sleep Arousal Scale (PSAS), and Quick Inventory of Depressive Symptomatology (QIDS), respectively. Serial mediation analysis adjusted for age and gender was performed, with indirect effects tested using 5000 bootstrap resamples; sensitivity analyses additionally adjusted for caffeine consumption and sleep medication use. Participants with depressive symptoms had lower MEQ scores and higher ESS and PSAS scores than those without (all p < 0.001). Eveningness was associated with greater depressive symptoms both directly and indirectly through daytime sleepiness and pre-sleep arousal. Eveningness retained a significant direct effect (69% of the total effect), indicating partial mediation. Pre-sleep arousal showed the strongest indirect effect (21.1% of the total effect), followed by the serial pathway through daytime sleepiness and pre-sleep arousal (5.6%) and daytime sleepiness alone (4.3%). Results were similar after additional adjustment. Daytime sleepiness and pre-sleep arousal partially mediated the relationship between eveningness and depressive symptoms, with pre-sleep arousal emerging as the strongest pathway. Interventions targeting bedtime hyperarousal may help reduce depressive symptoms in evening-type individuals, alongside approaches addressing other contributing mechanisms.