Sleep and Depressive Symptoms in the Morningness/Eveningness-Suicidal Ideation Relationship Depend on School Shift in Mexican Adolescents

The aim was to analyze the morningness/eveningness (M/E) effect on suicidal ideation through sleep and depressive symptoms mediators with school shift (i.e., morning and afternoon) as moderator. In this study, 586 Mexican adolescents, with a mean age of 16.31 ± 0.92, from a public high school in a double-shift school system (298 from the morning shift and 288 from the afternoon shift) participated. Measurements of sleep, morningness/eveningness (circadian preference), depressive symptomology, and suicidal ideation were completed. Adolescents in the afternoon shift reported a later rise time, bedtime, greater time in bed sleep length, and less social jet lag than in the morning shift. Considering the moderated-mediated analysis, circadian preference and suicidal ideation were mediated by both depressive symptoms and school day’s sleep length in the morning shift. In the afternoon shift, no mediation effect was significant. When weekend sleep length was considered in the model, only depressive symptoms had a mediating effect between circadian preference and suicidal ideation in the morning shift; no significant mediating effect was found on the afternoon shift. The results suggest that an afternoon school schedule may act as a protective factor for the adolescent’s mental health and may represent a viable option for future interventions.