Chronotype and suicide: The mediating effect of depressive symptoms

Background: Chronotype is individual characteristic, and people who stay up late are acknowledged to be more likely to experience depressive symptoms as well as impulsivity and suicide. Depression is also associated with suicidality. The purpose of this study was to investigate and analyze the role of depression in its effects on chronotype and suicidality. Method: A total of 5632 university students were recruited as participants. We evaluated their chronotype, depressive symptoms, and suicidality using questionnaires. Correlation analysis, analysis of covariance, and path analysis were performed. Results: Depressive symptoms and suicidality were higher among individuals with an eveningness chronotype: the greater the depressive symptoms, the higher the suicidality. The results of path analysis showed that the direct effect of suicidality in relation to chronotype was not statistically significant, but the indirect effect of depressive symptoms was statistically significant. This result indicates that depressive symptoms fully mediated the relationship between chronotype and suicidality. Conclusion: Morningness may be a protective factor, not only against depression but also against suicide. To assess the risk of suicide, we must evaluate not only depressive symptoms, but also the effects of chronotype on depressive symptoms.