The two-thirds of U.S. teenagers who get less than eight hours of sleep on school nights are more likely to smoke, drink and fight, according to a new study by the Centers for Disease Control and Prevention.
In a survey of more than 12,000 teens, 68.9 percent reported that they sleep less than eight hours on an average school night.
In 10 of 11 categories, those students were more likely to engage in risky behavior than students who sleep more than eight hours on school nights, the study found.
Those behaviors include smoking cigarettes and marijuana and drinking alcohol. For example, 50.3 percent of students who slept less than eight hours reported drinking alcohol in the prior 30 days, compared to 36.7 percent of those who slept more than eight hours.
Students who slept fewer hours also were less likely to exercise, more sexually active and more likely to fight and contemplate suicide. They were more likely to use computers more than three hours a day as well.
Sleep-deprived teens did not watch more television than their counterparts, the study concluded.
The study, published online by the Preventive Medicine journal, is believed to be the first large, national survey of its kind, the CDC said.
Lack of adequate sleep can be a warning sign for parents that their teens have other problems, the study's lead author told Reuters on Monday.
"I definitely wouldn't ignore it," said Lela McKnight-Eily, a clinical psychologist and epidemiologist at the CDC. "I think it's important for parents and adolescents themselves to both be aware of the issue and what can be associated with it."