sleep. Gamma-amino-butyric acid, or GABA, encourages sleep, and melatonin cues winding down in anticipation of sleep. While we are just beginning to understand the highly complex functioning of the sleep-wake cycle at a biochemical level, we do know that it is the dynamic balance of these neurotransmitters in pathways deep in the brain, plus the summary effect they have on a regulatory brain region called the hypothalamus, that puts us at a particular point along the sleep-wake continuum at a particular point in time. Behavior, genetics, light, and the myriad changes associated with puberty also influence the set point for sleep onset.

Children who haven’t yet gone through puberty receive these neurochemical sleep-wake signals at times appropriate to, and synchronized with, the day-night cycle. For example, their melatonin production is set in motion in the late afternoon as daylight fades, triggering the onset of the process that eventually produces sleep. Adolescents who have embarked on the puberty trail, however, receive these hormonal signals later in the evening, even though they require the same amount of sleep as their prepubertal friends. Teenagers and younger 20-somethings naturally stay up later because their pineal gland secretes melatonin later, which causes them to fall asleep later than children and adults. Studies done by eminent sleep researcher Mary Carskadon also suggest that the later secretion of melatonin may cause teens to sleep on and on in the morning.

The delayed sleep phase of adolescence.