Abstract
In a sample of early post-menarchal female adolescents, this study examined sleep regularity in relation to depression symptoms, circadian rhythms, and chronotype preference. Sixty-six female adolescents, aged 11-14 and within fifteen months post-menarche, completed a one-week sleep and circadian rhythm assessment involving self-reported sleep behaviors, 24-h sleep monitoring using wrist actigraphy, and serial cortisol and 6-sulfatoxymelatonin collections for four days. Sleep regularity was operationalized as the probability of being in the same wake/sleep state at any two timepoints 24 h apart (i.e., sleep regularity index (SRI)). Reduced SRI was associated with higher depressive symptoms (F [1,273] = 18.65, p = < .0001), as were eveningness chronotype (F [1,273] = 21.13, p = < .0001), sleep duration (F [1,273] = 6.25, p = .01), and self-reported life stress (F [1,273] = 22.82, p = < .0001). The interaction between SRI and chronotype was also a predictor of increased depression (F [1,273] = 18.65, p = < .0001), such that eveningness and low sleep regularity predicted higher scores. Sleep regularity was not significantly associated with cortisol awakening response, cortisol slope, or overnight melatonin levels. Sleep regularity appears linked to altered mood in early post-menarchal girls. Further research linking sleep regularity to physiological processes governing sleep is warranted. Interventions targeting sleep regularity stand to improve mental health outcomes, as well as promote healthy developmental trajectories for affect regulation.