The Teenage Brain

You don’t have to suffer to suffer to be a poet. Adolescence is enough suffering for anyone. — American poet John Ciardi, 1962

In his speech at the launch of the 1997 I Am Your Child campaign, director and actor Rob Reiner stated that “by the age of ten, your brain is cooked.” And until recently, most child experts, including Dr. Spock, would have agreed. They considered the first few years of a child’s life to be the most important — and the experiences a child had during those years to play a crucial role in defining the kind of person he or she would ultimately become. That understanding also helped create a whole generation of obsessively child-focused parents, who, with the best of intentions, have tried to cram a lifetime of “educating” into a few short years, subjecting their unwitting fetuses to a diet of Eine kleine Nachtmusik and their pre-verbal toddlers to basic arithmetic and multiple viewings of Baby Einstein dvds. (A wise elementary-school principal once noted, “I very much doubt Einstein was doing any of this when he was young.”)

Somewhere along the line, or so many of us believed, the window of opportunity would close. The foundations of the adult-to-be would be laid, and the worst damage would be done. The majority of brain development does, in fact, take place in the early years, when billions of synaptic circuits that will last the child’s lifetime are forming. But growth and change don’t end there. Important developmental changes, scientists are discovering, are still taking place in a big way through the adolescent years — and into the mid-twenties. Perhaps this helps to explain the growing phenomenon of adult children who linger on under the parental roof; their growing may not be over, despite their arrival at “adulthood.”

In recent years, researchers have finally been able to get real insight into the workings of the brain thanks to magnetic resonance imaging (mri), using the technology to map blood flow to the areas of the brain that are activated by exposure to various stimuli. By scanning the same group of adolescents over a period of years or by comparing the brain responses of teenagers to those of adults, researchers are putting together a portrait of adolescence that confirms what many parents have always suspected: adolescents might as well be a whole different species. They are, as one neuroscientist puts it, a “work-in-progress.”

Over the past decade, scientists have started to grasp exactly how distinctive the adolescent brain is and how crucial the years between ten and twenty- five are in terms of its development. And their discoveries have implications not only for parents, educators, and the medical community but also for policymakers. “I wouldn’t disagree with Rob Reiner that the first three years are important,” says Jay Giedd, chief of brain imaging in the child-psychiatry branch of the National Institute of Mental Health in Bethesda, Maryland. “I would just say that so are the next three and the next three and the next three, up to twenty-five and perhaps even beyond.”

This news may not come as a surprise to the mother who still lies awake at 3 a.m., waiting for her basement-dwelling, twenty-two-year-old post-grad son to come home. What science suggests is that “adulthood” as we have defined it doesn’t necessarily signal the end of childhood development — or of parental worries.

If the media is to be believed, the stereotypical teen is a selfish, volatile, rude, rebellious hormone-head, capable of little more than taking outrageous risks, ingesting too many harmful substances (legal and otherwise), committing crimes, crashing parties, trashing houses, and generally being a layabout. Of course, this is a gross misrepresentation: many teenagers pass through adolescence smoothly and happily, without becoming parents themselves, dropping out of school, or acquiring a criminal record instead of a degree. Still, there’s a stubborn tendency in the culture to ascribe every negative teen moment to “hormones.” Recent brain research, however, relieves hormones of much of the blame for this period of “storm and stress,” as psychologist G. Stanley Hall, father of adolescent research, called it.

The full extent to which hormones actually influence adolescent behaviour remains unknown. So is what role they play in brain development. Hormones are certainly responsible for the most obvious hallmarks of puberty; at some mysterious point in a child’s life, a protein called kisspeptin causes the hypothalamus — an area in the brain that orchestrates certain autonomic nervous-system functions — to secrete the gonadotropin-releasing hormone, which sets the pubertal changes in motion. Ultimately, estrogen and testosterone are responsible for the physical transformations — breast and genital development, body-hair growth, deepening of the voice, and so on — but by no means all the behavioural changes of adolescence. Hormones may have nothing to do with the fact that your daughter can’t bear your singing voice, for instance; it’s a safe bet, however, that a teenager’s fixation on sex and social standing is pretty much hormone related.

But puberty does have an impact on how they think. For instance, as Giedd points out, boys fairly predictably base their decisions on the question “Will this lead to sex? ” Giedd adds: “They may not say it in that way or it may not be that blatant, but if you just sort of go with that model it works pretty well.” When girls make decisions, he adds, they are more likely to keep the social group, and their place in it, in mind. But Giedd feels that puberty’s influence doesn’t extend much outside that realm. “Your ability to do a logic problem or to do geometry or to do other things seems to be more [related to] age itself.” Researchers have also found that the onslaught of testosterone in both male and female adolescents at puberty literally swells the amygdala — the brain centre associated with the emotions. Perhaps we can blame the amygdala for the slammed doors and sudden tears that overcome previously sunny children when they hit adolescence.

So hormones are not the only players in the changes that characterize adolescence. And while it is difficult to tease out the varying roles played by chromosomes, hormones, and other factors in teen behaviour, the insights that mri reveals are nothing short of astounding.