Teens do need more sleep than adults, but they rarely seem to get it. In addition, teens' natural body clocks tend to lead them to a later sleep phase than adults.
Teens should be getting around nine hours of sleep each night, and some might need even a bit more. In contrast, adults require around seven to eight hours of sleep each night. Despite these recommended sleep times, teens are often tired because they aren't likely getting the full night's sleep their bodies need. One study found that fully 90 percent of teens aren't getting nine hours of sleep a night. In fact, 10 percent of the teens studied weren't even getting six hours of sleep a night [Source: Mayo Clinic]. Some of the reasons for this are easily identified: Between school activities, social lives and part-time jobs, teens can often be overbooked. They simply have too much going on during the day to leave nine out of 24 hours for sleep. In some cases, the lack of sleep could be an indication of an underlying medical problem, such as depression, sleep apnea, medication side effects or narcolepsy.
Another reason for teens' chronic tiredness that is getting more attention is the early-morning starting time of many high schools -- some as early as 7:30 am. Medical professionals note that the internal body clock (called circadian rhythms) of teens shift dramatically toward going to sleep late and waking up late. Teens aren't forcing themselves to stay up late enough to catch David Letterman -- their natural sleep clock isn't releasing the melatonin they need to make them sleepy until around 11 pm or later. As a result, the forced early hours of schools can be a major contributing factor to the sleep deprivation of teenagers. The lack of sleep by teens can lead to a number of adverse consequences, such as poor grades, bad decision making, traffic accidents, moodiness, and physical problems.