Why do you think teenagers face more behavioral risk factors than any other age groups?

Less experience in life means teens have fewer opportunities to learn from their own mistakes and the mistakes of others. After all, when you're a kid your parents try to make sure you're always safe, and generally they succeed. So kids get to thinking that nothing really bad will ever happen to them because so far Mom and Dad have kept them safe. But teenagers have more opportunities to get into much deeper trouble--the kind Mom and Dad can't always save you from.

Another thing: the teenage brain has not developed and matured yet. Even when it's the same size as an adult brain, the parts of the brain that deal with self-control and predicting consequences of certain actions are not done growing yet.

I think part of the answer is empowerment. Doing bad or risky things proves to yourself that you are in control, that you have free will to change your own destiny. It's not a good or smart way to feel empowered, but I think that's part of the motivation for taking such risks.