Recent studies at the National Institute of Health (NHI) using MRIs have shown that the areas of the brain responsible for evaluating risk don't fully develop until the age of 25.
We often see teenagers exhibit impulsiveness, feelings of invincibility, and sucumbing to peer pressure. These are all signs of immaturity in cerebral development, and in most cases, will decrease with age. See this external article for more reading on the subject.
I know that as I've aged, I've forgotten more than I thought I knew when I was younger. It's like that old German saying "Too soon old, too old smart". Youth is definitely wasted on the young.
It's too bad we can't be like Mearth from the Mork and Mindy show - born old and age backwards. Then when we as adults make stupid decisions without considering the consequences, we'd have something to blame it on.
