Many students in all the studies also reported increased daytime sleepiness. Just as in the United States, high schools in other countries start early in the morning—in Brazil they begin between 7:00 and 7:30 and in Israel at 8:00—leaving night owls exhausted as well as at risk for health and behavior consequences. According to researcher Amy Wolfson, teenagers in developed countries average a little over seven hours of sleep on school nights—a far cry from the eight and a half to nine and a half hours they should be getting.

What effects does this sleep deficit have on teens internationally? In China, a study of 1,538 adolescents revealed that regular nightly sleep of less than seven hours was significantly associated with increased behavior problems. In Italy, a study by Flavia Giannotti of 14-to 20-year-olds showed a correlation between increased daytime sleepiness, increased vulnerability to accidents, increased use of stimulants and tobacco, sleep problems, and anxiety. A survey of 1,457 Korean students revealed a progressive decrease in total sleep time from grades 5 to 12 of three hours on weeknights and one hour on weekends. Tenth graders averaged 6.02 hours of sleep on weeknights and twelfth graders just 4.86 hours. The study showed evidence of major detriments to functionality with symptoms of daytime sleepiness, depressed mood, and problem sleep-wake behavior.

Stress, just as it is in the United States, also is linked to sleep deprivation in other parts of the world. Israeli researcher Avi Sadeh has found that sleep is quite sensitive to emotions, expectations, and anxi-