The Summary: "A National Institutes of Health study suggests that the region of the brain that inhibits risky behavior is not fully formed until age 25"
This is interesting along with an article I saw a few years ago that said that: The reasoning portion of the human brain doesn't fully develop until age 16.
Now, you may ask, why is this significant? Well, people nowadays have a problem raising children. Too often they think of their kids not as children (with the associated brain development) but and miniture adults that are perfectly capable of making the right decisions based on reason. The brain development studies should show that, children are, in fact, incapable of making clear, reasonable decisions and should be treated as, well, children.
Here's a good article on the subject:
What were they thinking? Youths' brains seen as factor in fatalities