What Keeps Night Owls Well During the Week? Sleep Onset Consistency as a Moderator Between Morningness-Eveningness and Adolescent Development.

Objectives: A preference for eveningness - one's perception of being most alert later in the day - is associated with negative developmental outcomes in adolescence. Sleep onset consistency is protective against such outcomes. Toward a more nuanced understanding of relations between sleep-wake processes and adolescent development, we examined weeknight sleep onset consistency as a moderator of relations between eveningness and multiple indicators of development. Method: A sample of 272 high-school students (Mage = 17 years, SD = 9.12 months; n = 133 identified as female; 41% non-Hispanic Black/African-American, 59% non-Hispanic White/European-American) participated in a week of at-home sleep actigraphy assessment in 2017-2018. Adolescents reported their morningness - eveningness, internalizing symptoms (depression, anxiety), positive affect (optimism and subjective happiness), and physical health, and mothers reported on youths' behavior problems. Relations were examined between morningness - eveningness and each indicator of development; sleep onset consistency was examined as a moderator of these associations.

Results: On average, adolescents with a preference for eveningness had higher levels of externalizing behaviors and internalizing symptoms and lower levels of positive affect and physical health compared to peers with a preference for morningness (Bs = -0.27*-0.12***). Each association was moderated by weeknight sleep onset consistency. Across all indicators of development, evening-preferring youth with more consistent weeknight sleep onset had 0.49-0.72 SD better outcomes on average than evening-preferring youth with less consistent weeknight sleep onset.

Conclusions: Falling asleep at roughly the same time each night can protect adolescent night owls from behavior problems and internalizing symptoms and can promote their positive affect and physical health.