You could be putting yourself and others at risk for serious injury. To make matters worse, because teenagers are relatively inexperienced drivers, they are unlikely to recognize their degree of fatigue. As most of us have experienced, you're much more likely to snap at your family and friends when tired. Girls are especially vulnerable to depression once sleep deprivation sets in. Being tired makes it a lot harder to make clear-headed decisions about drugs and alcohol.
Tired teens are more likely to be swayed by peer pressure.
Also, to stay awake, many use caffeine, nicotine and other stimulants, which in turn cause them to fall asleep later and awake more tired than ever. Your circadian rhythm is your internal sleep-wake clock. Basically, some people have more energy in the mornings, some in the afternoons, and some are full of pep after midnight. Dr. Carskadon's research has shown that biological changes during puberty affect a teenager's circadian rhythm. Because of this, many teens are not ready to fall asleep until 11 PM or later.