Adolescent Brain

The biological processes underlying adolescent brain maturation may not produce favorable results, even when external variables are favorable. Maturation errors reveal that the adolescent brain is undergoing major structural and functional rearrangement and if the reconstruction is flawed, the emerging young adults are dysfunctional and may be disabled for life.  

Modern parents of teenagers will often doubt that they have any role to play except to offer custodial support and then recognize that their jurisdiction is limited. Teenagers have a tense mix of old primitive features in their mind and new modern ideas. They tend to manifest ancient clan behavior and at the same time develop individual, modern personalities. Adolescent society is stratified, competitive and relatively unforgiving. Teenagers cluster in small groups with strict inclusion/exclusion rules. They manifest ancient animal and human social patterns spontaneously and the importance of group affiliation with their peers often takes precedence over family affiliation. Family values and teenager group values often conflict and the conflict is seldom resolved in favor of the family unless parents are loving, determined, and on the job 24 hours a day.

For decades, literature has described and decried the alienation of adolescents from their parents and a host of studies has confirmed that peer group dynamics influence teenagers more than their parents. Teenagers "hang-out" together and spontaneously form groups that drift toward the periphery of the adult society. Typically, deviant, antisocial and criminal behavior emerges as a group expression. Even "nice" teens routinely experiment with sex and other forbidden pleasures, commit minor felonies, conceal their activities from parents and teachers and lie when confronted with suspicions.

Puberty changes the entire programming manifest by children and raises the ante so that the relatively safe play of younger children is replaced by the more dangerous and consequential play of teenagers. Parents are often unprepared for the major transformations that occur after puberty and feel estranged from the new person emerging awkwardly and contentiously in their own home. The powerful force behind adolescent maturation is ancient biology and is not a product of the local community or contemporary social values. The powerful forces of change are under genetic control and are strongly influenced by the chemistry and other physical properties of the environment. Ideal conditions for a teenager would combine the best custodial features of an extended family, a clean home, proper food, clean air, exercise and recreational opportunities in natural environments. 

Ideal conditions are uncommon, even in affluent communities and the recipe for healthy teens breaks down at the physical level of bad food, bad chemicals and noisy chaotic environments. Bad chemicals are in the food supply, the air and are purposefully ingested, inhaled and injected by adolescents. Bad chemicals produce bad brain function.

The key feature of brain maturation and learning appears to be the pruning of neuronal connections that are not required. Maturation involves differentiation of mental ability, specialization and loss of the randomness that so characterizes children's activities. The pruning of neuronal connections appears to occur in stages and continues through adolescence. One idea of neuronal pruning is to make often-used circuits more efficient by removing circuits that are not being used. A final wave of circuit pruning in adolescence may account for some of the problems young people have adjusting to themselves and the world they live in. Not only is their body changing rapidly, their world changing rapidly but also their brain is reprogramming itself in midstream.

The period of synaptogenesis and pruning extends from just before birth through adolescence. During Phase 4 of synaptic pruning (early youth to prepuberty), the number of synapses is stable but synapse reorganization occurs. Phase 5 of synaptic development starts around puberty and is characterized by synaptic pruning; 30%–40% of synapses are removed. In the best case, this reorganization leads to a stable adult synaptic network.  In the worst case, this pruning could disable the individual and sometimes lead to schizophrenia or some other mental illness.

With repeated MRI scans, Giedd et al revealed increased cortical thickness during childhood followed by thinning of the cerebral cortex that proceeds from the back to the front during adolescence. As the cortex thins, the underlying myelin content of the white matter increases. Giedd suggested that effective pruning increases brain efficiency and that superior intelligence correlates with an initial accelerated, prolonged phase of cortical increase in children followed by equally vigorous cortical thinning by early adolescence.    The pruning process is dynamic and profound.

Errors in pruning are inevitable in some teens, but little is know about the kind of errors that occur. We can only speculate that some teens are lucky and emerge better brains and others are unlucky and emerge with brains that do not function well.

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Human Brain in Health and Disease

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The Human Brain in Health and Disease, 2010, is a Persona Digital Book. We encourage readers to quote and paraphrase topics from Human Brain in Health and Disease published online and expect proper citations to accompany all derivative writings. The author is Stephen Gislason and the publisher is Persona Digital Publications. The date of publication is 2010. The URL to the book description is Human Brain