Linear and Nonlinear Associations between Sleep and Adjustment in Adolescence

ABSTRACT

Background & Objectives

A growing body of work supports linear associations between sleep and socioemotional adjustment in adolescence. However, associations between sleep and adjustment are not necessarily linear and investigations of nonlinear effects are scarce. This study examined linear and nonlinear relations between several sleep-wake parameters and externalizing behavior and internalizing symptoms in adolescence, and assessed the role of adolescent sex as a moderator of effects.

Participants

Participants were high school students (N = 180; M age = 17.49, SD = .62; 59% female; 68% White/European American, 32% Black/African American) from a wide range of socio-economic backgrounds living in semirural communities and small towns in Alabama.

Methods

Sleep-wake parameters were indexed by actigraphy-derived sleep minutes and adolescents’ reports on morningness-eveningness (circadian preference), sleep-wake problems (sleep quality), and sleepiness. Adolescents completed questionnaires on externalizing behaviors and internalizing symptoms.

Results

Controlling for sleep duration, a higher preference for eveningness and poor sleep quality were associated in a linear fashion with increased externalizing and internalizing symptoms. Nonlinear relations between sleepiness and internalizing symptoms emerged with pronounced sex-related effects, including somewhat delayed accelerating relations for males and rapidly accelerating associations that tended to plateau for females.

Conclusions

Results illustrate the importance of examining multiple sleep-wake and adjustment variables as well as linear and nonlinear associations.

Acknowledgments

This study was supported by funding from the Eunice Kennedy Shriver National Institute of Child Health and Human Development (R01-HD046795) awarded to M. El-Sheikh. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health. We wish to thank our participants and the lab staff, most notably Bridget Wingo and Lori Elmore-Staton, for data collection and preparation.

Disclosure statement

No potential conflict of interest was reported by the authors.

Notes

¹ The present study is distinct from El-Sheikh et al.’s (2019) with younger children and the two studies are based on two entirely independent samples.

² We also examined whether a linear and a nonlinear term of actigraph-measured sleep efficiency, or the interactions between sleep efficiency and adolescent sex (linear x sex interaction and nonlinear x sex interaction), were related to externalizing and internalizing symptoms, but no significant associations emerged.

³ We also fit the models excluding sleep minutes and compared them to those that covaried sleep minutes. The statistical significance of the two sets of models did not vary and there were only slight variations in coefficient values.

Additional information

Funding

This study was supported by funding from the Eunice Kennedy Shriver National Institute of Child Health and Human Development [R01-HD046795] awarded to M. El-Sheikh.