Depression - The Teenage Brain

Excerpted from
More Than Moody; Recognizing and Treating Adolescent Depression
By Harold S. Koplewicz, M.D.

Anna Freud was half right. It would be abnormal-maybe even impossible-for a teenager to breeze through adolescence on an even emotional keel. Being moody and crabby are as much a part of the territory as pimples and proms. To a certain degree, they can't help themselves: it's virtually a biological necessity. Where Freud was wrong was in her assertion that there's something wrong if a teenager doesn't get depressed-and that no matter how moody she gets, no matter how sad she becomes, it's all more or less normal and it doesn't constitute any kind of mental illness.

In adults as well as younger people, brief unhappiness is indeed a normal human condition, sometimes triggered by a disturbing event. But when that depression doesn't go away, when it lasts more than a few days or weeks and interferes with a person's ability to function-that's when it crosses into the category of biological disease. Depression among adults is very common and well documented. Studies suggest that one woman in five and one man in ten can expect to develop it during their lives. With the advent of medications that mysteriously rebalance brain chemicals that regulate mood, treatment of depression has been revolutionized in the past decade. In the memorable phrase of Elizabeth Wurtzel that served as the title of her book about her own youthful depression, we are a Prozac Nation. Yet depression is often not thought of as a real disease, especially in the case of children and adolescents.

The whole idea of depression in young people has evolved in psychiatry over the last century, particularly in the last two decades. Earlier generations believed that adult-style depression could not exist in children because they didn't have the emotional or cognitive maturity of adults. What began to change the perception of adolescent depression from a myth to a real disorder were studies showing that while depression among the young has some distinct features, many of its symptoms and effects are similar to what adults experience. Moreover, it was found that even after recovering from the depths of a depression, many adolescents continue to have residual effects and are much more likely to have depression as adults. Eventually, clinical research found that treatments that work for adults-from antidepressant medications for serious depressions to cognitive behavioral therapy for milder cases-also work in adolescents.

These realizations were enough to convince the field that adolescent depression could not be dismissed as a normal, even necessary, passage. Now we know that the opposite is true: serious depression is the most common mental illness among teenagers, and research is starting to give us clues as to why. As if just being a teenager-or a parent of one-wasn't enough to worry about, it appears there may be solid biological reasons why adolescents as a group are especially vulnerable to depression during these critical years.

Every parent has to have wondered what on earth goes on in the head of a teenager. The answer is: a lot. Adolescence is nothing if not transition. Puberty changes everything from boys' voices to girls' self-image. We know all about those raging hormones. But there is a growing body of scientific evidence that the physiological changes of adolescence may be most dramatic in the chemistry and circuitry of the brain. Much has been said and written in recent years about the brain development that occurs in babies, from birth to age three. But there is fascinating new research showing that brain "remodeling" is nearly as dramatic during the teen years.

One researcher, Jay Giedd of the National Institute of Mental Health, has used a technique called Structural Magnetic Resonance Imaging (SMRI) to show changes in the shape and size of the brain during the early to mid-teen years. Studies have shown that the brains gray matter-where the higher intellectual functions are carried out-thins out with age. Giedd found that the gray matter thickens until age 11 in girls and 12 in boys. Unlike in infancy, when millions of new brain cells are constantly being created, what happens in later childhood is not the formation of new brain cells but an increase in the number of synaptic connections between the cells already there. In fact, that's what might make the gray matter denser. But just before adolescence, and continuing until about age 25, the gray matter is gradually "pruned," in a natural chemical process that clears out unused brain-cell connections to make the brain more efficient. It's analogous to driving in the country. There are plenty of roads to take, dozens of them, but they're not good roads. Eventually you come to a multilane superhighway. You leave behind the meandering and abundant dirt and gravel roads for the smooth, efficient pavement of the highway. In terms of cognitive development, it is the "use it or lose it" principle. As the brain prunes, a person gradually becomes more specialized in his abilities. That's why learning languages is relatively easy for children. They can learn just about anything, though depth comes only later. Their learning abilities are a mile wide and an inch deep.

Giedd's key finding was that the highest rate of pruning occurs from 14 to 17-as much as four times as high as during any other period. This means that there is a lot more structural change in the brain than was earlier thought.