Chronotype and Depression: Serial Mediation of Perceived Stress and Insomnia in a Two-Wave Three-Month Longitudinal Study.

Chronotype, a biological trait that determines an individual's sleep-wake preferences, influences depression risk. However, the psychological and behavioral mechanisms underlying this relationship have only been examined to a limited extent in longitudinal studies. Thus, this study aims to test the impact of chronotype on depression via perceived stress and insomnia, both separately and through serial mediation. The study uses data collected at three-month intervals via a two-wave longitudinal design to explain this relationship. The study included 234 participants (51 men and 183 women) with a mean age of 22.02 (range 18-49). Perceived stress, insomnia, and depression were measured at T2 for chronotype at T1. Path analysis results showed that chronotype negatively affected perceived stress and insomnia, which indirectly predicted depression levels. Perceived stress and insomnia play a role, both separately and serially, in the longitudinal relationship between chronotype and depression. The findings show that as morningness increases, perceived stress and insomnia decrease; consequently, the risk of depression decreases as well. It should be noted that the sample predominantly consisted of young adult female university students, which may limit generalizability. These results suggest that interventions targeting stress management and sleep quality, particularly for evening-type individuals, could effectively reduce the risk of depression.