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Much of the focus on insufficient sleep in adolescence has been on sleep duration and sleep quality—the average time spent asleep and how restful that sleep is. While both of those variables have been linked to cognitive functioning and emotional control, many studies, including our own (e.g. Buckhalt, El-Sheikh, & Keller, 2007) have shown that variability in sleep schedule is related to poor functioning in multiple domains. During school years, wake up times are fairly stable during the week, so the variability comes with going to bed at different times. For children who build up a sleep debt, both bedtime and wake up times are typically later on weekends. All of the body’s systems are dependent on timing regulated by the brain’s ”master clock,” the suprachiasmatic nucleus, and there are clock genes throughout the body that also determine timing of physiological processes. For example, the timing of melatonin release is associated with the feeling of sleepiness that induces sleep. Eating, exercising, and sleeping “off-time” is disruptive to the coordinated timing.
There is now evidence that sleep irregularity is associated with altered brain development in adolescents. In a paper just published in the journal Developmental Cognitive Neuroscience, Telzer and colleagues (2015) report on a study where adolescents’ sleep was measured at age 14 and again a year later. Then the adolescents underwent a brain scan, a diffusion tensor imaging (DTI) that enables measurement of neural integrity of white matter. During adolescence, gray matter (density, volume, and thickness) in the brain is reduced, and white matter, reflective of neural connectivity, is increased. Adolescents who had more variable sleep schedules a year earlier had less white matter in several brain areas. Interestingly, variability in sleep schedule a short time before the scan at 15 years was not related to brain development.
Adolescence is a time of tremendous social changes and also of significant organizational development of the brain. For adolescents to function optimally on a day to day basis, they need sufficient, regular sleep. This study suggests that poor sleep, especially regularity, may have long term deleterious consequences
Buckhalt, J. A., El‐Sheikh, M., & Keller, P. (2007). Children's sleep and cognitive functioning: race and socioeconomic status as moderators of effects. Child development, 78(1), 213-231.
Telzer, E. H., Goldenberg, D., Fuligni, A. J., Lieberman, M. D., & Galvan, A. (2015). Sleep Variability in Adolescence is Associated with Altered Brain Development. Developmental Cognitive Neuroscience, 14, 16-22.
