Song, at age 13, is experiencing a growth spurt. previously an early riser, he is still in bed at 10 a. m. if given the chance and not asleep until 1 a. m. these changes may be attributed to

Song may be experiencing changes in his diurnal and sleep-wake cycle. This is normal for teenagers and most tend to sleep later in the morning but have more energy towards the later hours of the night. This biological shift is created by the change in time that melatonin is released in their systems.