Impaired Brain Development

Recent research has found that the adolescent brain is a brain in transition. In fact, it continues to mature and change in very important ways until about age 24.

This maturation starts at the back of the brain in the cerebellum. This region of the brain influences physical coordination and sensory processing. It then moves towards the front from the nucleus accumbens which influences motivation, to the amygdala which influences emotion, and finally to the prefrontal cortex which affects judgment. In particular, judgment that involves resisting impulses or delaying gratification is still under construction during late adolescence and early adulthood.

The nucleus accumbens is the structure in the brain that directs our behavior when we are motivated to seek a reward. Because the nucleus accumbens in the teenage brain has not fully matured, there is a disconnect between how much effort one is willing to expend to acquire a reward. In general, teenagers tend to prefer activities that require relatively low effort yet produce high excitement.

The amygdala is the tiny, tucked away brain structure that helps us respond emotionally to our entire range of experiences. In adolescents, the maturing amygdale may be responsible for the automatic “hot” versus “cool” response and the propensity of youth to misread the neutral or inquisitive facial expressions of others as a sign of anger. They are more likely to feel that they live in a hostile or dangerous world than adults live in, and their “hot” response to this world may include fights or other aggressive behavior.

The prefrontal cortex aids in judgment and decision making. Located just behind the forehead, this structure is one of the last areas to mature. An immature prefrontal cortex is thought to be the neurobiological explanation for why teenagers show poor judgment and too often act before they think.

All of these structures are made up of nerve cells, also known as neurons. The growth of the brain’s neurons occurs through late childhood with over 1,000,000,000,000,000 possible connections. At around age 11 for girls and age 12 ½ for boys, some of these connections are pruned off. The pruning of the prefrontal cortex neurons produces a more efficient prefrontal cortex by young adulthood, meaning the ability to think more clearly and make judgments more efficiently. But during the pruning process, the brain is not functioning at full capacity.

Therefore, we can infer that during this developmental and pruning process, an adolescent may exhibit some of all of the following behaviors:

• A preference for sensation seeking and physical activity;
• Poor planning and judgment;
• Minimal consideration of negative consequences; and
• More risky, impulsive behaviors.

The adolescent brain is particularly vulnerable to the effects of binge drinking. Preliminary research has shown that the developing brain can be damaged by excessive alcohol use. , , ,

• Adolescent rats exposed to various amounts of alcohol have significantly more brain damage in their frontal cortex than their adult counterparts. They also show greater damage to their hippocampus, which affects the working memory. This means that it is harder for them to complete tasks that require them to remember one thing while doing another.
• With long-term alcohol use, adolescent rats have shown a massive loss of neurons in their cerebellum, basal forebrain, and neocortex. The loss represents a decreased ability for the various parts of the brain to communicate and coordinate with each other.
• Brain damage can occur even after a few days of "binge drinking." Rats given the equivalent of 10 drinks on two consecutive days damaged the part of their brains responsible for smell. It is suggested that damage to this part of the brain in rats is comparable the frontal cortex in humans which is involved in judgment and decision-making.
• Human adolescents with alcohol use disorders had nearly 10% less volume in the hippocampus, our primary brain structure for memory and learning. These adolescents have a more difficult time accessing their memories than their peers. It is not known if these effects are reversible.
• Binge drinking and other forms of substance abuse during adolescence increase the likelihood of experiencing psychological problems later in life.
• Repeated episodes of binge drinking during adolescence may lead to long-lasting deficits in cognitive abilities, including learning and memory. Frequent drinkers (100 or more total drinking sessions) performed more poorly than controls on several tests, including tests of learning, memory, and visuospatial functioning. Their studies suggest that heavy use of alcohol and other drugs during the teenage years predicts lower scores on tests of memory and attention when one is in their early-mid twenties.
  

The adolescent brain is a brain in flux. There are a number of important changes taking place during this stage of development. It is possible that repeated overexposure to alcohol alters the course of brain development in a way that might be hard to correct if the abuse persists throughout the adolescence period.

Repeated episodes of binge drinking during adolescence can negatively impact brain development. The following are important points to keep in mind:

• It is now quite clear that the brain undergoes a tremendous amount of development during the teen years, including a major remodeling of the frontal lobes, which are involved in planning, decision-making, impulse control, and language.
• Changes in the frontal lobes and other areas are influenced by experience, which means that the decisions that kids make can have a big impact on how their own brains develop.
• Healthy choices = healthy brains, unhealthy choices = unhealthy brains.
• Because of the changes occurring in the brain during the teen years, alcohol affects teenagers and adults differently – for instance, it appears to produce bigger impairments in learning and more widespread brain damage in adolescents than in adults.
• Repeated alcohol exposure might alter the trajectory, or path, of teen brain development.
• The moldability, or plasticity, of the brain decreases as we enter the early 20s, which means that we might not be able to make up entirely for the poor decisions that we make as teenagers.

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