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Inside the teenage brain
Tina Hesman
National Post? ?12-23-2005? ?
Researchers focus on defining 'normal' and track changes that may trigger mental disorders
The first peeks into the puzzling adolescent mind are revealing an organ in the midst of a near complete overhaul. The startling changes are partially responsible for teenagers' often erratic and risky behavior and may also harbor the seeds of mental illness.
The research has broad implications not just for parents and their teens but also for everyone who shares a part of their world - - at school, in the workplace, on the highways and the Internet. Policymakers will have to decide what to make of these findings as they ponder issues such as crime and punishment, educational testing programs, drug use and even video games.
To date, much of the discussion around teenagers has focused on why so many change from adorable children into sometimes-moody pre- adults.
But the latest research has focused on defining "normal" and tracking the changes that may trigger mental illnesses or strip the defenses of a mind already vulnerable to psychiatric disease. Knowing what's "normal" may lead to a tool that can predict which adolescent is likely to fall prey to depression, bipolar disorder, schizophrenia or a variety of other brain disorders.
The technology to predict who will get a mental illness is still years away, said Dr. Deborah Yurgelun-Todd, director of cognitive neuroimaging at the Brain Imaging Center at McLean Hospital and Harvard Medical School in Boston. And researchers are still struggling to pin down normal brain development. That's not an easy task, because the brain grows in fits and starts, and everyone develops a bit differently.
"For parents worried about their children getting labeled too young, I can sort of see that, because the indicators aren't hard and fast yet," Dr. Yurgelun-Todd said. "We have hints. We have suggestions of trends that seem to be more typical," but no definitive diagnostic test yet.
Teenagers' often inscrutable and erratic behavior has been dismissed as a product of a bath of sex hormones unleashed during puberty. That is about where research halted for a long time. Now scientists are learning that changes in the brain may play a bigger role in that behavior.
There is no question that the brains of people with schizophrenia and bipolar disorder look and work differently from those of their healthy peers, Dr. Yurgelun-Todd said. And those changes probably start earlier than most people suspect.
It now seems that "some people may be genetically ready to develop illness," but the defect does not become apparent until the brain matures, she said.
Dr. Judith L. Rapoport and her colleagues at the National Institute of Mental Health also have been searching for the roots of schizophrenia. For a decade and a half, they have repeatedly scanned the brains of people ranging from toddlers to adults. Along the way, they began to discover how normal brains mature.
The general layout of the brain doesn't change as people mature, Dr. Rapoport said. But the brain grows and shrinks, gets rewired and refined, parts are encased in protective coatings, brain cells die, and sex hormones and neurotransmitters flood in. This all happens under the influence of genetic and environmental blueprints designed to shape the organ into a brain ready for the responsibilities of adulthood.
The timing of the hormonal surges and brain changes with the onset of mental illnesses probably aren't coincidental, researchers say. One theory holds that because brain structures involved in emotion are developing in the teenage years, the brain is more susceptible to emotional disturbance at that time.
The details of normal brain development are still just sketches. What goes wrong in the brain during mental illness is even more unclear. The portrait that is emerging is drawn in grey and white. Grey matter and white matter, that is.
Take a slice of the brain and the outer layer appears grey, while most of the middle is a mass of white. They are both composed of brain cells.
The grey matter is the cell bodies of neurons, the brain cells responsible for processing information. Long projections, called axons, extend out from the cell body of the neuron and connect it to other brain cells, like the cables that link computers in an office. The axons are wrapped in fatty protective coating called myelin.
The axons with their myelin sheaths make up the white matter.
White matter growth accelerates in the teen years and continues into adulthood. The "growth" is actually the result of myelin encasing the brain's connecting wires.
The earliest parts of the brain to get wrapped in myelin are the parts that control movement and language -- skills young children need, said Dr. Henry Nasrallah of the University of Cincinnati College of Medicine. But some parts of the brain don't really come online until the teen years, he said.
Among the last areas to become fully wired are the frontal lobes and temporal lobes. Those parts of the brain are significant because they control abstract thinking, impulsiveness and emotion.
The fact that teenagers' brains aren't mature has led many people to ask whether teens can be held fully accountable for their actions, Dr. Yurgelun-Todd said last month in an address at the annual meeting of the Society for Neuroscience in Washington. The research could influence debates about whether the death penalty should be imposed for crimes committed by teens, whether kids are responsible enough to drive at 16 and whether 18-year-olds are ready to vote.
Dr. Melissa P. DelBello, co-director of the Bipolar Disorders Research Program at the University of Cincinnati, and her colleagues have been peering into the white matter of the brain. In teenagers with bipolar disorder, the white matter is disorganized, particularly in the frontal regions, the researchers found.
Since those regions govern impulse control and attention, and help regulate emotion, disruptions there can produce erratic behavior.
While the white matter is being wrapped in its protective coating, the grey matter of the brain is undergoing its own changes. Inefficient or confusing connections between neurons, called synapses, are pruned and some cells die.
From the ages of about 14 through 16, people lose about 20% of the synapses in the brain, Dr. Nasrallah said.
This loss of grey matter, he said, is "like a company laying off 10% of its workers and still being profitable and efficient."
The pruning may actually help the brain work better.
Children have more overall brain activity than adults, probably because they use their brains less efficiently than adults do, said Dr. Deanna M. Barch, an associate professor in the Department of Psychology at Washington University.
"It's almost like they need more brain than an adult to perform the same task," Dr. Barch said.
In schizophrenia, the pruning process doesn't work the way it should and doesn't allow for specialization, Dr. Barch said.
Some areas of the brains of people with schizophrenia are less active than in healthy adults, but overall, their brains are more active, she said.
Working memory -- the type of memory that lets you hold a phone number in your head for a few minutes and contributes to long-term memory -- is defective in people with schizophrenia, Dr. Yurgelun- Todd said.
"If this is missing, it's going to put people at a disadvantage for being able to read their world and respond," she said.
That can be particularly crippling during adolescence when skills for social interaction, intuition and nuance are emerging, she said.
Dr. Rapoport's studies showed that children with early-onset schizophrenia rapidly lose grey matter from the frontal and temporal lobes, and they lose more grey matter than their healthy peers.
But the way to slow the process is unclear. It could involve medicating children who display warning signs of schizophrenia but don't yet have the illness.
Dr. Yurgelun-Todd said, "We have no problems taking aspirin to prevent heart disease or vitamins to prevent colds, so if you know you're going to get a devastating brain disease, maybe it's not so bad to take a drug."
And drugs may not even be necessary to head off mental illness, she said. Simple changes in the way children are raised could be as effective.
"The human brain is very susceptible to its environment, both positive and negative," she said.
Some people think censoring movies, TV and video games could help promote mental health in youngsters. But it may be more important that families provide stimulating activities, good role models and a supportive environment for their children, Dr. Yurgelun-Todd said.
Researchers hope that learning to control the rush of neurochemicals and hormones and shape brain development could help cure mental illness. Dr. Yurgelun-Todd said she is optimistic that science will soon be able to diagnose mental illness at its earliest stages, but she doesn't have confidence that society will embrace the changes necessary to minimize the ravaging effects the brain disorders can have on young minds.
Tina Hesman
National Post? ?12-23-2005? ?
Researchers focus on defining 'normal' and track changes that may trigger mental disorders
The first peeks into the puzzling adolescent mind are revealing an organ in the midst of a near complete overhaul. The startling changes are partially responsible for teenagers' often erratic and risky behavior and may also harbor the seeds of mental illness.
The research has broad implications not just for parents and their teens but also for everyone who shares a part of their world - - at school, in the workplace, on the highways and the Internet. Policymakers will have to decide what to make of these findings as they ponder issues such as crime and punishment, educational testing programs, drug use and even video games.
To date, much of the discussion around teenagers has focused on why so many change from adorable children into sometimes-moody pre- adults.
But the latest research has focused on defining "normal" and tracking the changes that may trigger mental illnesses or strip the defenses of a mind already vulnerable to psychiatric disease. Knowing what's "normal" may lead to a tool that can predict which adolescent is likely to fall prey to depression, bipolar disorder, schizophrenia or a variety of other brain disorders.
The technology to predict who will get a mental illness is still years away, said Dr. Deborah Yurgelun-Todd, director of cognitive neuroimaging at the Brain Imaging Center at McLean Hospital and Harvard Medical School in Boston. And researchers are still struggling to pin down normal brain development. That's not an easy task, because the brain grows in fits and starts, and everyone develops a bit differently.
"For parents worried about their children getting labeled too young, I can sort of see that, because the indicators aren't hard and fast yet," Dr. Yurgelun-Todd said. "We have hints. We have suggestions of trends that seem to be more typical," but no definitive diagnostic test yet.
Teenagers' often inscrutable and erratic behavior has been dismissed as a product of a bath of sex hormones unleashed during puberty. That is about where research halted for a long time. Now scientists are learning that changes in the brain may play a bigger role in that behavior.
There is no question that the brains of people with schizophrenia and bipolar disorder look and work differently from those of their healthy peers, Dr. Yurgelun-Todd said. And those changes probably start earlier than most people suspect.
It now seems that "some people may be genetically ready to develop illness," but the defect does not become apparent until the brain matures, she said.
Dr. Judith L. Rapoport and her colleagues at the National Institute of Mental Health also have been searching for the roots of schizophrenia. For a decade and a half, they have repeatedly scanned the brains of people ranging from toddlers to adults. Along the way, they began to discover how normal brains mature.
The general layout of the brain doesn't change as people mature, Dr. Rapoport said. But the brain grows and shrinks, gets rewired and refined, parts are encased in protective coatings, brain cells die, and sex hormones and neurotransmitters flood in. This all happens under the influence of genetic and environmental blueprints designed to shape the organ into a brain ready for the responsibilities of adulthood.
The timing of the hormonal surges and brain changes with the onset of mental illnesses probably aren't coincidental, researchers say. One theory holds that because brain structures involved in emotion are developing in the teenage years, the brain is more susceptible to emotional disturbance at that time.
The details of normal brain development are still just sketches. What goes wrong in the brain during mental illness is even more unclear. The portrait that is emerging is drawn in grey and white. Grey matter and white matter, that is.
Take a slice of the brain and the outer layer appears grey, while most of the middle is a mass of white. They are both composed of brain cells.
The grey matter is the cell bodies of neurons, the brain cells responsible for processing information. Long projections, called axons, extend out from the cell body of the neuron and connect it to other brain cells, like the cables that link computers in an office. The axons are wrapped in fatty protective coating called myelin.
The axons with their myelin sheaths make up the white matter.
White matter growth accelerates in the teen years and continues into adulthood. The "growth" is actually the result of myelin encasing the brain's connecting wires.
The earliest parts of the brain to get wrapped in myelin are the parts that control movement and language -- skills young children need, said Dr. Henry Nasrallah of the University of Cincinnati College of Medicine. But some parts of the brain don't really come online until the teen years, he said.
Among the last areas to become fully wired are the frontal lobes and temporal lobes. Those parts of the brain are significant because they control abstract thinking, impulsiveness and emotion.
The fact that teenagers' brains aren't mature has led many people to ask whether teens can be held fully accountable for their actions, Dr. Yurgelun-Todd said last month in an address at the annual meeting of the Society for Neuroscience in Washington. The research could influence debates about whether the death penalty should be imposed for crimes committed by teens, whether kids are responsible enough to drive at 16 and whether 18-year-olds are ready to vote.
Dr. Melissa P. DelBello, co-director of the Bipolar Disorders Research Program at the University of Cincinnati, and her colleagues have been peering into the white matter of the brain. In teenagers with bipolar disorder, the white matter is disorganized, particularly in the frontal regions, the researchers found.
Since those regions govern impulse control and attention, and help regulate emotion, disruptions there can produce erratic behavior.
While the white matter is being wrapped in its protective coating, the grey matter of the brain is undergoing its own changes. Inefficient or confusing connections between neurons, called synapses, are pruned and some cells die.
From the ages of about 14 through 16, people lose about 20% of the synapses in the brain, Dr. Nasrallah said.
This loss of grey matter, he said, is "like a company laying off 10% of its workers and still being profitable and efficient."
The pruning may actually help the brain work better.
Children have more overall brain activity than adults, probably because they use their brains less efficiently than adults do, said Dr. Deanna M. Barch, an associate professor in the Department of Psychology at Washington University.
"It's almost like they need more brain than an adult to perform the same task," Dr. Barch said.
In schizophrenia, the pruning process doesn't work the way it should and doesn't allow for specialization, Dr. Barch said.
Some areas of the brains of people with schizophrenia are less active than in healthy adults, but overall, their brains are more active, she said.
Working memory -- the type of memory that lets you hold a phone number in your head for a few minutes and contributes to long-term memory -- is defective in people with schizophrenia, Dr. Yurgelun- Todd said.
"If this is missing, it's going to put people at a disadvantage for being able to read their world and respond," she said.
That can be particularly crippling during adolescence when skills for social interaction, intuition and nuance are emerging, she said.
Dr. Rapoport's studies showed that children with early-onset schizophrenia rapidly lose grey matter from the frontal and temporal lobes, and they lose more grey matter than their healthy peers.
But the way to slow the process is unclear. It could involve medicating children who display warning signs of schizophrenia but don't yet have the illness.
Dr. Yurgelun-Todd said, "We have no problems taking aspirin to prevent heart disease or vitamins to prevent colds, so if you know you're going to get a devastating brain disease, maybe it's not so bad to take a drug."
And drugs may not even be necessary to head off mental illness, she said. Simple changes in the way children are raised could be as effective.
"The human brain is very susceptible to its environment, both positive and negative," she said.
Some people think censoring movies, TV and video games could help promote mental health in youngsters. But it may be more important that families provide stimulating activities, good role models and a supportive environment for their children, Dr. Yurgelun-Todd said.
Researchers hope that learning to control the rush of neurochemicals and hormones and shape brain development could help cure mental illness. Dr. Yurgelun-Todd said she is optimistic that science will soon be able to diagnose mental illness at its earliest stages, but she doesn't have confidence that society will embrace the changes necessary to minimize the ravaging effects the brain disorders can have on young minds.
