Sleep deprivation is a common problem for teenagers. Some have suggested that the solution to the problem is to start the school day later, although the real world often demands an early wake-up call, especially for students who work or have other commitments after school. A study at Johns Hopkins University found that teens who started school at 9:30am performed better academically than their counterparts who started at 7:30am. A likely reason for this was that the weekday bedtime for the 9:30 group was shifted two hours closer to their weekend bedtime, making it easier for them to readjust their internal sleep-wake clocks each Monday.
Even when it is possible to start the school day later, the problem is often not resolved. Over time it becomes increasingly difficult for many kids to get up even for a 9:30 class, because there is a strong tendency to stay up later and later, especially on the weekends. These are often the same students who try to avoid taking classes that meet before noon when they go off to college.
The vicious cycle of trying to catch up on sleep on the weekend- only to have the problem recur on Monday morning- is related to the fact that bedtime starts advancing later and later in the fall as the amount and intensity of light decreases. The underlying problem is often seasonal depression, manifested in oversleeping, reduced energy, carbohydrate cravings, and sometimes increased anxiety and trouble concentrating. In New England, where a summer day can be twice as long and thousands of times brighter than a day in winter, it is not uncommon to see a winter pattern of near-reversal of day and night in teenagers. Of course, when oversleeping or other problems persist into the spring, factors other than seasonality may be involved, but without morning light of adequate intensity, "seasonal" teenagers cannot keep the biological clock that controls the wake/sleep cycle from being reset at a later time each day in the fall and winter- the intensity of natural daylight at that time of year is inadequate to do the job.
I met an Alaskan teenager who has a serious problem with lack of sleep every winter; he also gets very irritable in the fall and has rage attacks during the winter months that are out of character the rest of the year. This young man travels to Costa Rica each January, where his symptoms disappear because the intense light and earlier dawn resets his biological clock almost immediately. Unfortunately, the problems return when he returns home to the still-dark Alaskan winter. Incidentally, I have noted that teenagers in Costa Rica, where the sun rises and sets at about the same time year-round, rarely have problems with sleep deprivation, although their bodies require just as much sleep at this developmental stage as their age mates everywhere in the world.