Abstract Introduction Evening chronotypes often experience misalignment with societal schedules and increased feelings of isolation, particularly at night. Although loneliness and mental health difficulties are common in this group, the role of nocturnal loneliness remains unclear. This study examines how chronotype, nocturnal loneliness, and general loneliness relate to mental health. Methods Participants (N = 442) were recruited through Prolific and completed an online Qualtrics survey assessing demographics, chronotype: Morningness-Eveningness Questionnaire (MEQ), general loneliness: UCLA Loneliness Scale 3 (LS), nocturnal loneliness: Nocturnal Loneliness Scale (NLS), and self-rated mental health (0–100). Mediation analyses were conducted using PROCESS Model 4 to test whether NLS and LS independently mediated the association between chronotype and mental health rating. Parallel indirect effects were estimated using 5,000 bootstrap samples with 95% confidence intervals. Results Individuals with a later chronotype reported poorer mental health (r = .33), higher nocturnal loneliness (r = –.22), and higher general loneliness (r = –.30). In the full mediation model, both forms of loneliness were uniquely associated with poorer mental health (nocturnal loneliness: b = –2.95, p = .001; general loneliness: b = –9.88, p .001). Both mediators contributed significant indirect effects: nocturnal loneliness (indirect = 0.063, 95% CI 0.020, 0.117) and general loneliness (indirect = 0.279, 95% CI 0.180, 0.387). The total indirect effect was significant (indirect = 0.342, 95% CI 0.229, 0.456). The direct effect of chronotype on mental health remained significant (b = 0.309, p .001), indicating partial mediation Conclusion These findings demonstrate that individuals with a later chronotype experience poorer mental health partly because they report greater loneliness, including both general loneliness and loneliness experienced at night. Although both forms of loneliness mediated the chronotype–mental health association, general loneliness accounted for a larger portion of the indirect effect, while nocturnal loneliness contributed a smaller but still significant unique pathway. These results highlight the importance of considering both daytime and nighttime social experiences when examining mental health disparities among evening types. Assessing and addressing loneliness, particularly the challenges that arise at night, may represent a meaningful intervention target for improving wellbeing in people with later chronotypes. Support (if any)
Harlow et al. (2026) studied this question.