Human Growth and Development / Unit 9 HGD 1208 worked example, 60 to 90 seconds
Sleep and the Phase Delay
The idea
Teens aged thirteen to eighteen are recommended eight to ten hours of sleep a night, yet most US high-school students report getting too little. Growth hormone is secreted mainly in deep sleep. The circadian rhythm is the body's daily biological cycle, and Mary Carskadon and colleagues found that puberty brings a phase delay: a shift toward later sleep and later waking, tied to the timing of melatonin release and to light sensitivity.
In practice
A sixteen-year-old wide awake at eleven at night and barely able to function at seven in the morning, sleeping about two hours longer on weekends.
Where people slip
The misconception is that teenagers who sleep late are lazy. The shift is biological, driven by puberty's effect on the body clock. Even mild sleep loss raises the risk of accidents, poorer learning and memory, aggression and low self-esteem.
Your place on the trail
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