New research shows that the frontal lobe of the brain, the areas responsible for judgment and the ability to consider consequence, may not be fully developed until the early twenties. In addition, the nucleus accumbens (an area that has to do with impulsivity and responds somewhat with the idea “that felt good, so lets do it again”) is more active in adolescence.
This combination is consistent with what we often see and fear in teens, the impulsive, risk taking teenager. Is this an excuse for parents to say there is nothing they can do to prevent their teen from doing bad things? No, it is not. What this does mean is that parents and their supervision is needed even more than previously thought.