School Start Time Conference - Session 02:

Developmental Changes to Sleep Biology Affect Adolescent Sleep - Mary A. Carskadon, PhD

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Great in-depth explanation of the research.
— Conference Attendee

Mary Carskadon, PhD, Professor, Department of Psychiatry and Human Behavior and Adjunct Professor of Cognitive, Linguistic and Psychological Sciences, Alpert Medical School, Brown University

Dr. Carskadon’s presentation focuses on the biological causes of the delay in sleep timing that occurs during adolescence, whereby the natural sleep-wake cycle shifts later in the day.  Dr. Carskadon explains that the human brain undergoes enormous structural changes during adolescence and discusses the changes that occur in the circadian timing system and the homeostatic system that regulate sleep.  To underscore the biological source of this change, Dr. Carskcadon notes that a sleep-timing delay also occurs during adolescence and pubertal onset in other species of mammals. 

Dr. Carskadon presents research that demonstrate that the release of melatonin, “the hormonal gateway to sleep," shifts later in the day during adolescence, while the amplitude of the melatonin signal falls.  Research has also found that adolescents experience a greater sensitivity to evening light, associated with  a delay in circadian timing.  

As it relates to homeostatic drive, or sleep pressure, Dr. Carskadon  presents research measuring slow brain wave activity and sleep propensity showing that the homeostatic system also undergoes significant changes during adolescence, resulting in a slower accumulation of sleep pressure during the course of the day.

The conclusion is that sleep’s two main bio-regulatory systems both undergo changes during adolescence that operate to shift the natural sleep-wake cycle later in the day.


Mary A. Carskadon, PhD
Professor of Psychiatry and Human Behavior and Adjunct Professor of Cognitive, Linguistic and Psychological Sciences at Brown University, Mary Carskadon received a BA in psychology from Gettysburg College (1969) and is a distinguished alumna of that institution. She holds a doctorate with distinction in neuro- and biobehavioral sciences from Stanford University (1979), earned under the mentorship of William C. Dement, MD, PhD. Dr. Carskadon’s current research includes evaluating how sleep and circadian timing influence smell, taste, food choices, and food consumption in overweight and normal weight teens and development of “smart lighting” to improve academic outcomes in secondary school students. Her awards include a Lifetime Achievement Award from the National Sleep Foundation and an Outstanding Educator and Distinguished Scientist Award from the Sleep Research Society.  She is an elected Fellow of the Association for Psychological Science and Fellow of the American Association for the Advancement of Science.