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Scientists have begun finding evidence that alcohol and cigarettes are even worse for teen-agers than you might assume. Throughout the teen-age years, an adolescent brain goes through major remodeling. It's being shaped by biology and by a young person's experience. The evidence now suggests the alcohol and cigarettes may have an especially damaging effect on those developing brains. Michelle Trudeau reports.
MICHELLE TRUDEAU reporting:
Although a teen-ager's brain is about the same size as an adult's, it is qualitatively quite different because it's not yet finished. Three major brain regions are still under construction: the frontal lobes, the hippocampus and the cerebellum, regions where nerve cells are rapidly growing intricate branches and making millions of new connections throughout the teen years. Neuroscientist Aaron White, from Duke University, studies adolescents.
Mr. AARON WHITE (Neuroscientist, Duke University): Some of the most important changes take place in the frontal lobes and are critically involved in our decisions that we make, our goals, our dreams, our aspirations, controlling our impulses. And the frontal lobes are really in a state of intense flux during the teen-age years.
TRUDEAU: And alcohol, White is finding, is toxic to these developing frontal lobes.
Mr. WHITE: You've got the circuitry that's not really online yet to help you make good decisions and control your impulses. And so, you add alcohol to a teen-age brain and they tend to make worse decisions and have even more trouble controlling their impulses.
TRUDEAU: Much of White's research focuses on teen-age binge drinking, youngsters who consume five or more drinks at a time. Binge drinking is extremely common among teens; much more than in adults, White has found. Teen-agers drink infrequently, but when they drink, they drink a lot and chug it down very quickly. `A common result,' White says, `is alcoholic blackouts.' Different than passing out, during a blackout a person is fully awake, interacting, making decisions, operating in the real world. But unbeknownst to the teen-ager, not all the brain is functioning.
Mr. WHITE: The part of the brain that's supposed to be keeping a record for what you are doing isn't working.
HARRIS: The hippocampus, where new memories are made.
Mr. WHITE: And so, what alcohol does is shuts down that part of the brain, and if you drink fast enough and reach a high enough blood alcohol level, it seems to be able to shut it down to such an extent that you wake up the next day and you don't remember what you did.
TRUDEAU: A blackout in memory of events and actions that occurred the previous evening while drinking. `Now while alcohol can cause blackouts in everyone, animal studies,' White adds, `suggests that a teen-ager's brain is much more vulnerable than an adult's to alcohol's attack on the memory center.'
Mr. WHITE: The data suggests that the younger we are, the more sensitive those areas of the brain are to alcohol, and alcohol not only shuts off the ability of the brain to make new memories, but it also seems to have a potent effect on limiting the birth of new neurons in the hippocampus.
TRUDEAU: Researcher Ron Dahl, from the University of Pittsburgh, says there's yet another important brain region that's still under construction in teens.
Mr. RON DAHL (Researcher, University of Pittsburgh): There's growing evidence that one of the areas that is very late developing into late adolescence is the cerebellum.
TRUDEAU: `The cerebellum,' says Dahl, `is known for being in charge of coordination, motor control, balance and that alcohol dramatically disturbs this area.' Try walking in a straight line when intoxicated. But there's now new evidence that this region in the back of the brain does a lot more.
Mr. DAHL: What we've learned is the cerebellum has a much broader role in cognition and emotion and all kinds of complex behavior. And the fact that the cerebellum is very sensitive to alcohol effects, and the fact that the cerebellum is very late developing, raises a lot of red flags about youth drinking.
TRUDEAU: Researcher Aaron White adds that the younger one starts to drink, the greater the likelihood that person will go on to have a diagnosable alcohol disorder.
Mr. WHITE: We now know that the adolescent brain is in a state of constant flux, and we know that when the brain is developing like that, alcohol does nasty things to it. So is there a safe level of drinking for teen-agers? We don't know. And so, for me, it's an issue of: Why risk it?
TRUDEAU: A message for teens comparable to the message given to pregnant women that there is no safe level of alcohol on a developing fetus. Aaron White believes there may be no safe level of alcohol on the developing teen-age brain.
The other drug commonly used by teen-agers is nicotine in cigarettes. Here, too, researchers are finding evidence that nicotine is particularly harmful to the developing brains of teens. Research psychiatrist Leslie Jacobsen from Yale University's School of Medicine.
Ms. LESLIE JACOBSEN (Research Psychiatrist, Yale University School of Medicine): We studied 41 adolescent tobacco smokers who were regular smokers. These smokers smoked, on average, 12 cigarettes per day.
TRUDEAU: Boys and girls, 14 to 18 years old, were given memory tests by Jacobsen to check what's called `verbal working memory,' a type of memory coordinated by those still developing frontal lobes, and very relevant for students.
Ms. JACOBSEN: It's a kind of memory that is important in, for example, paragraph comprehension. When you're reading a paragraph you need to be able to remember what the sentence said at the beginning of the paragraph in order to understand the whole paragraph by the time you are done reading it.
TRUDEAU: So a critical type of memory for reading comprehension. Jacobsen compared the memories of the teens who smoked with teen-agers who had similar backgrounds, but who did not smoke.
Ms. JACOBSEN: Regardless of how recently the smokers had smoked, they performed worse on the working memory task.
TRUDEAU: She also found that the age at which a person took up smoking affected memory.
Ms. JACOBSEN: The earlier the teen started smoking, the worse their memory performance was.
TRUDEAU: And boys, because they typically begin smoking earlier than girls, did worse on the memory tests and on another test as well.
Ms. JACOBSEN: The male smokers had worse divided attention, and that's the test where they have to process visual and auditory stimuli at the same time. So when they hear and see something, they have to be able to think about it at the same time. And the male smokers did worse, and the only difference between the female and the male smokers is that the boys started smoking at a younger age.
TRUDEAU: Jacobsen points out that these deficits in memory and attention were quite subtle, not glaring impairments. However, she speculates...
Ms. JACOBSEN: When faced with really difficult academic tests, like the SATs or other difficult tests that a lot of kids encounter, this could potentially interfere with their maximal performance.
TRUDEAU: And parallel evidence from studies with animals shows that nicotine is a neurotoxin. That is, nicotine kills cells; specifically, in brain areas critical for learning and memory.
Ms. JACOBSEN: It's commonly believed by young people that the ill effects of smoking don't really start until you're in middle age. These data really don't support that, and the animal data don't either. The case is growing stronger and stronger that nicotine is bad for the brain while you're developing.
TRUDEAU: Jacobsen's study was recently published in the journal Biologic Psychiatry. The studies on teens and alcohol by Aaron White and Ron Dahl appeared last June in the Annals of the New York Academy of Sciences. This research is some of the first to investigate the impact of nicotine and alcohol on a teen-ager's developing brain and, as such, serve as preliminary clues of a unique kind of damage these drugs may cause to teens.
For NPR News, I'm Michelle Trudeau.
INSKEEP: This is NPR News.
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