What is the number one killer of teenagers?

Number one killer of teens is driving under the influence.
Teens often get drunk or high at parties, after which they sit in a car and drive, not really thinking about the consequences, and the consequences can be dire. Not only are they putting their own life at risk, but they are also risking the lives of the people who are with them in the car, as well as those people that may be involved in a car crash thanks to them.