Teenagers are three to four times more likely to die during those years than at any other point past infancy, until they become elderly. The causes of death are largely attributed to their higher risk-taking and accidents. What may appear to be bad judgment or selfishness may really be an inability of their incompletely formed brains to think before they act.
Reasoning along with judgment, goal planning, risk assessment, consequence prediction, organizing, and prioritizing are the “executive functions” that are controlled from the last part of the brain to mature. Their mature bodies and growing independence are ready to go, but teens’ prefrontal cortex has yet to literally “get it together”. This is a setup for disaster. Just when they are becoming sexually active, have access to drugs and alcohol, and begin to drive, teens neural network hubs for those judgment and risk-assessment controls are still childlike.

Bad Judgment from Child Brains in Adult Bodies

The prefrontal cortex has an anatomic location that enables it to integrate a wide array of neural circuits into a functional whole. This process of integration enables the prefrontal area to play a central role in complex mental processes that emerge as the child grows. The prefrontal region is crucial for social cognition (understanding the minds of others), self-regulation, response flexibility (taking in data, pausing, reflecting), and accurate self-awareness. So as teens experience pressures from peers, parents, and society as they strive to create their individual identities, the prefrontal cortex, with its neural network of executive functioning and judgment, is not in place to guide them.
Without the prefrontal cortex’s executive functions to inhibit impulses, weigh consequences of decisions, prioritize, strategize, separate fact from opinion, weigh the validity of information, and analyze risk, teens make decisions based on emotional, reactive, rather than logical, reflective, responses. Until these networks are mature, things adults consider obvious and even dangerous may not be interpreted that way by the still incomplete frontal lobes of teenagers.

The Adolescent Growth Spurt……It’s Also In Their Brains
The brain’s learning is coded in patterns and stored in neurons in the cerebral cortex. This outer brain layer, with the greatest density of information-storing neurons, is called gray matter because neurons are darker than most other cell structures in the brain. Although the cortex is a relatively thin layer and comprises only about 17% of the brain’s volume, if it were unfolded it would spread over 500 square inches.
The neurons are connected to one another by over one million nerve fibers in the adult brain, with each neuron making from 1,000 to 50,000 connections with other neurons. Most of these connections are dendrites, the branches that sprout from neurons to connect to neighboring neurons and carry information at speeds up to 300 feet per second. Dendrites carry information as electric current into the neurons and axons carry information away. Myelin is the insulating coating that builds up around the most active axons. Throughout life the brain changes by both expanding and pruning these connections between cells, keeping the connections that are used the most and efficiently pruning away the unused ones.
One of the most active periods of brain reorganization occurs around two years of age, when a huge build up of neural connections is followed by a massive pruning that allows the strongest and most used connections to function more effectively. During adolescence, the frontal lobes undergo a second wave of reorganization and growth. This growth appears to represent millions of new synapses (connections between the brain cells).
Although it may seem like the more synapses and connections, the better, the brain actually consolidates learning by pruning away the least-used pathways, which in turn allows the brain to operate more efficiently. It is in the later teens and early twenties that a massive pruning of these excess connections begins and continues at a slow rate until the pruning tapers off in early adulthood.

Multit-ASKING for Trouble
Teens from 16-20 have the highest fatality and injury rates, with motor vehicle crashes the number one cause of death from ages 15-20. There are about 8,000 teen motor vehicle deaths a year and 28% of teen drivers killed in motor vehicle crashes are intoxicated at the time of the accidents.
The brain’s judgment development delay is not just problematic regarding excessive drinking and drunk driving. During this age period the driving risks are exceeded by poor decisions about seatbelts, talking on cell phones, and texting. Drivers are less likely to use seat belts when they have been drinking. Of the young drivers who had been drinking and are killed in crashes, 74% are unrestrained and 55% of passenger vehicle occupants who die are not wearing seat belts.
Driver inattention is the leading factor in most crashes and near-crashes. Nearly 80% of crashes and 65% of near-crashes involved some form of driver inattention within three seconds before the event. Driving while talking on a cell phone is as dangerous as driving under the influence of alcohol (four times more impaired than sober driving) and texting is eight times more dangerous than sober/undistracted driving. (Recall the accident on the California train where the driver was texting while driving, killing himself and about 25 others.)
Even adult brains sometimes cannot handle two simple tasks as easily as we think they should. For example, while seated in a chair rotate your right foot clockwise. Then draw the number 6 in the air with your right hand. Your right foot will change to moving counterclockwise. With teen judgment underdeveloped, their confidence in their abilities exceeds that of adults and puts them at greater risk for overconfidence when doing things that require focused alertness.

The Brain is a Pleasure-Seeking Organ
Dopamine is the chemical neurotransmitter most prominent in the brain’s emotionally responsive and reactive limbic system; and dopamine is a pleasure surging chemical. Risk-taking itself increases dopamine levels and the associated pleasure response, as do many “recreational” drugs. Teen’s “ungoverned” brains want to feel pleasure and may direct behaviors to pump up the dopamine surge artificially and temporarily by using drugs or engaging in risky behavior.
Addictive drugs such as cocaine and amphetamine cause a several-fold increase in dopamine levels in the brain. The combination of this high pleasure response from dopamine joined with the immaturity of the frontal lobes increases susceptibility to illegal drug use, fast driving, dangerous biking or skate boarding activities, alcohol abuse, binge eating, sexual promiscuity, and other dangerous activities. Almost 20% of high school students surveyed reported having carried a weapon (gun, knife, or club) one or more days in previous 30 days.

What Can Parents and Teachers Do?
Parents and teachers can inform adolescents about the potential risks such as drugs, alcohol, sexual promiscuity, and eating disorders, and other risk-taking behaviors that do bring about a pleasurable dopamine jolt. But, to make the information stick, teens need knowledge about their own brains to add impact to those warnings. Teens benefit from teachers’ and parents’ explanations of the brain’s chemistry and physiology and by understanding their brain’s susceptibility to high-risk behaviors. They can use this knowledge, while they develop their internal logic systems, to better defend themselves against dangerous temptations.
The main threats to adolescents' health are the risk behaviors they choose. A National Longitudinal Study of Adolescent Health followed over 12,000 adolescents from grades 7 through 12 and concluded that parent-family connectedness, perceived school connectedness, and high expectations regarding school achievement were protective against many high-risk behaviors. These family and school influences, plus teaching teens about their brains, can be the protective factors that save the life of many teens.

As a neurologist and teacher I wrote a “Brain Owner’s Manual” to share with teens which is available on the Psychologytodayonline.com website.
http://www.psychologytoday.com/blog/radical-teaching/200904/your-brain-owners-manual