The development of the adolescent brain

Why are teenagers so moody?

Pre-adolescent brain development

In the two or three years leading up to puberty the brain develops millions of new neurons, particularly in the pre-frontal cortex (the area at the front of the brain) and the grey matter surrounding.  Just as with the young child, it is important that these new neurons are used and so for the young adolescent this is often a period of trying new hobbies, activities or new experiences in order to ensure that these connected to the existing brain structure.  Many parents are not aware of the importance of this period in brain development and so may miss this opportunity.  This period is commonly referred to as the ‘use it or lose it’ stage of brain development.

Brain development during adolescence

The brain begins work at the back and works forward, eventually seizing the opportunity to effectively reduce the working capacity of the frontal lobes as it hard wires in the new neurons utilised in the previous growth stage and then cull the unused neurons.  As we’ll discuss in the next section, the frontal lobes are the region that control personality, behaviour, risk analysis and our value system.  This, combined with a huge increase of hormones in the brain, leads to a very sudden and unexpected change in personality and social skills.

You will notice an increase in risk-taking and emotional based behaviour as the amygdala responds without the guiding voice of the frontal lobes.  Demands on them or questions will often be perceived by the mammalian brain as a threat and will result in a confrontational response or refusal.  Stress levels increase a cortisol rises in the brain.  Problems, chores or learning that their brain could cope with now present more stress for the teenage brain as the frontal lobes dealt with those in the past.  Their brain craves stimulation and reward, so you will see an increase in mobile phone and computer use.

At the same time the need for sleep returns to a similar level as the brain required the last time it went through this process, during the first 2-3 years of its life.  Melatonin, the hormone released in our brain to trigger the sleep cycle is released up to two hours later in the day.  This has an impact on the sleep cycle, as the second part of our sleep, the REM or Rapid Eye Movement stage, which is normally from about 2am to 6am, is longer and later in the morning and frequently interrupted by the need to get up for school or college.  Alcohol misuse during this time is shown to interrupt the vital development of the adult brain.

Brain development after adolescence

As the frontal regions of the brain are reconnected the brain experiences a sudden rush of new thinking abilities.  As the freshly exposed neural pathways are used the brain further strengthens and speeds up the connections through further myelination.  A learning or educational growth spurt often happens at this time.  Sleep patterns return to their normal routines and personality is restored, often with a new set of individual beliefs.  The brain continues to learn how to use its new abilities during the latter teenage years and into the twenties.

This is the stage when values and beliefs systems are independent of their parents and teachers.  New ideas and standards are set in the emerging adult brain and the teenager will often reassess the future they seek as adults.

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