One in three high school students reported they had texted or emailed while driving during the previous 30 days, according to the centers' 2011 youth risk behavior survey of 15,000 high school students.

The percentage of those who had texted or emailed while driving was higher for upper classmen, with nearly 43 percent of 11th graders and 58 percent of 12th graders saying they had done so in the past month. This is the first time texting questions were included in this survey.

"Texting or emailing while driving a car can have deadly consequences," said Howell Wechsler, director of the CDC's Division of Adolescent and School Health.

The CDC did not have statistics on how many teens are killed annually from accidents caused by texting or emailing.

In 2010, auto accidents killed 3,115 teens aged 13-19, the CDC said. That was down 44 percent over the past decade, but auto accidents remain the leading cause of teen deaths.

The centers said the survey revealed more teenagers are wearing seatbelts and fewer are driving after drinking.

Over two decades, the percentage of high school students who never or rarely wore a seatbelt declined from 26 percent to 8 percent, the CDC said.

In 2011, only 8 percent of students said they had driven a car within the past 30 days when they had been drinking alcohol, compared to 17 percent in 1997. The percentage of students who rode with a driver who had been drinking during the previous 30 days dropped from 40 percent to 24 percent.

"These trends show that we are making great progress," Wechsler said.

The risk behavior survey found that while cigarette smoking dropped slightly from 2009-2011, more teens smoked marijuana, with 23.1 percent of students saying they had used it one or more times during the previous 30 days. For the first time since the CDC began taking the survey in 1991, more teens said they smoked marijuana than cigarettes.

Nearly 40 percent of students said they had at least one alcoholic drink in the previous 30 days.

The risk survey also found that one in five students said they had been bullied on school property during the previous 12 months. About 16 percent said they had been bullied electronically through email, chat rooms, instant messaging, websites or texting.

(Editing By Colleen Jenkins and Vicki Allen)

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