Why our brains ‘turn red’ in teenage years

During and after puberty the human brain undergoes a brutal change. This profound reorganisation, along with numerous hormonal, physical and psycho-social consequences, is often misunderstood by adults.

Published 10 Mar 2022, 11:57 GMT, Updated 10 Mar 2022, 12:58 GMT
The concert was unlike any Austin Brown (centre) had attended—a dance party called Dayglow where blasts ...

The concert was unlike any Austin Brown (centre) had attended—a dance party called Dayglow where blasts of fluorescent paint rained down on crowds in downtown Austin. Black light made them shine. “If you weren’t dancing, you were just standing there covered in paint,” Brown said. “That doesn’t sound like fun.” The hunt for novelty can go awry when teens try to top each new kick with another, more intense one. But it also helps them find their path. A concert-goer since high school, Brown now studies lighting design in college. This photograph originally appeared in the October 2011 issue of National Geographic magazine as part of a feature on the teenage brain.

Photograph by Kitra Cahana, National Geographic

“ANY STRONG EMOTION will release the panda”, warns the mother of Mei Lee – the protagonist of new Pixar movie Turning Red. Mei Lee is a 13-year-old girl, outgoing and funny, torn between being a model daughter for her very protective parents, and the personal chaos of adolescence. The ‘panda’ – while literally a large, red creature into which she transforms as soon as she is overwhelmed by an emotion – symbolises both change and renewal.

In Asian cultures, the panda represents the value of emotions and the importance of patience. A motto for any teenager, and a metaphor for this very peculiar period of life, when everything is renewed and redefined. (The Walt Disney Company is majority owner of National Geographic.)

“It is often said that the teenager is both a child and an adult, but it would be more accurate to say that they are no longer a child and not yet an adult. It is as if your child goes into their room one night and comes out as a different person the next morning. This very rapid change surprises not only parents but also the teenagers themselves. It is this in-between period without any reliable reference that constitutes the essence of the adolescent ‘crisis’” explains Philippe Hercberg, a psychiatrist and former lecturer at the Paris XIII Faculty of Medicine and now working in San Fernando, Spain.

A physical and psychological ‘moult’

Adolescence really begins when the pituitary gland and hypothalamus, neuroglandular organs located in the brain, begin to produce specific hormones that stimulate the secretion of testosterone and oestrogen.

Growth then accelerates, by an average of 8 centimetres per year in girls and 10 centimetres per year in boys. Only in the first year of life can such a speedy growth rate be observed in humans: a baby gains an average of 20 centimetres during its first year of life.

First fine, then thicker hair appears all over the body. The clitoris develops, the penis grows and lengthens. The hips and thighs widen. The voice becomes deeper.

In addition to hair and bodily changes, hormonal changes have significant effects on the psychic aspect and on the social and emotional behaviour of teenagers. Using recent non-invasive dynamic brain imaging techniques, researchers have been able to understand important processes in brain development between the ages of 10 and 20. During this period of life, the brain undergoes a profound reorganisation. The connections and functions of its structures change, only fixing in the first half of our thirties. This renewed plasticity, which is very much like the connections that are made in the first years of life, is an opportunity to rectify the imbalances observed in early childhood. It is also a phase of great vulnerability. "It is both an opportunity to relive and overcome previous developmental stumbling blocks. But it’s also a complicated period, if the feeling of internal security that should have been built up during childhood is not sufficiently established," explains Nancy Pionnié-Dax, head of the child psychiatry unit at the Erasme Hospital in the Paris region, France.

As in the first months of life, especially during the phase known as ‘childhood adolescence’ – a pivotal period for the child also known as the ‘terrible twos’, the brain retains only the most frequently used connections. “At the age of two, a first period of ‘separation-individuation’ can be observed. The child, having perceived that he and his mother are two different persons, will test the limits, [...] to exist outside his mother: he will start to say no, to explore alone, to oppose... Adolescence is considered as a second phase of separation-individuation. The child, becoming this time pubescent, cannot remain stuck to his parental objects and is pushed by the pubertal development, the cerebral maturation to separate himself, physically and psychologically from his parents,” adds Nancy Pionnié-Dax.

Myelination of axons (white matter), a sort of brain cable several times thinner than a human hair, increases during adolescence. Processes within the brain become faster and more efficient. The structures of sensory perception mature early during puberty, but the areas of the prefrontal cortex, which allow us to plan, prioritise, weigh the pros and cons and control our impulses, mature last. The control centre of the brain (prefrontal cortex) – humorously depicted in the film Inside Out – is dominated during adolescence by the reward system. This is even more emphasised in situations where the teenager is with people of their own age. We then feel more reckless, more emboldened, the novelty stimulates more than it frightens, the risk is less well evaluated.

“There is a sudden change in the brain's architecture during adolescence. It changes throughout childhood, but during adolescence the limbic system develops much more rapidly than the prefrontal cortex.” explains Philippe Hercberg. “The posterior maturity of the prefrontal cortex comes at the end of adolescence. This is why the search for immediate reward is not counterbalanced by a form of control during this period… [and] why we observe a lot of risky behaviours and the beginnings of addictions in teenagers. It is a period of vulnerability, particularly to disinhibiting substances that affect the production of dopamine.”

Their “fight club” had rules. At least one Friday a month, boys gathered after school in the backyard of Bryan Campbell (at far left) to wrestle and box. Campbell’s mother gave her OK as long as they kept it safe; a bloody nose was the worst injury suffered. The boys often used phones to film their contests, then posted the videos to a private group on Facebook, where more friends could admire their prowess. The rush of a headlock, a bond between friends, their fights delivered both excitement and social rewards. This photograph originally appeared in the October 2011 issue of National Geographic magazine as part of a feature on the teenage brain.

“This results in impulsiveness, a need for immediacy, a search for sensations and pleasures, without worrying about long-term effects,” says Nancy Pionnié-Dax. “There is nothing more incomprehensible for a teenager than to be told to ‘make a plan’ when he or she wants something. Waiting is very complicated, it's the immediacy that is the most important.”

Far from the broad caricature that the adolescent crisis is a simple rebellion against the established order and authority figures such as parents, perhaps it is necessary to study (or remember) how upsetting these physical changes can be.

Constant upheaval

Once adolescence is over, only women and people undergoing hormonal treatments will be subjected to such upheavals, notably during their menstrual cycles, pregnancies, during pre-menopause and menopause.

Beyond the hormonal side of the story, which is a sort of infinite whirlwind, an essential question arises in adolescence: “Who am I?” Who am I in relation to others and for the others? What is my place in this constantly changing world? Adolescents must accept their new bodies, integrate them into their self-image, define their gender identity, their sexual identity, their cultural and religious identity, develop their own values, become more autonomous and answer the anxious question of their education and professional future. So many unknowns to which answers must be found in a relatively short time. Any adult would feel overwhelmed by this constant upheaval.

“Adults have a great deal of difficulty understanding and accepting teenagers,” reckons Philippe Hercberg. “They no longer remember that they were once teenagers. The difficulty lies in the ability of adults to read and decipher the problems of adolescence, which is what so frequently provokes reactions of opposition, even rejection.”

“There is nothing more incomprehensible for a teenager than to be told to ‘make a plan’ when he or she wants something. Waiting is very complicated – it's the immediacy that is the most important.”

Nancy Pionnié-Dax

“Parents are aware of the stakes, the risks, and would like to ‘spare’ or ‘protect’ their teenagers. But teenagers need to experience this new autonomy, sometimes by turning it against themselves. [...] Adolescents make us experience emotions that mirror what they are experiencing: anxiety, impatience, sometimes badly controlled emotional outbursts. It is very difficult to find the right distance! And some scientific articles have shown that the degree of emotionality of a teenager talking with his parents about a sensitive subject is such that their cortex is completely turned off,” says Nancy Pionnié-Dax.

It is also a period during which relationships and their value change. The cards are somehow redistributed in all the social groups that are the family, friendship, social and love spheres, a form of psychosocial moult. A new balance is established, a pendulum between narcissism and what psychologists call the object relationship: the investment in oneself and the investment in the others.

So how, in spite of the pubertal changes, can one remain ‘one’s self’ (if one already knows who he or she is)? One theory is that in spite of the new rhythm imposed by their body, the teenager must maintain a certain continuity in their relations to the world and to others.

“The adolescent needs the group and the look of others. It is one of the groups that has suffered the most from the multiple lockdowns. They often function by mimicry, out of fear of being rejected by the group, even if the group will not necessarily reject them if they do not smoke or drink like the others,” argues Philippe Hercberg. “We believe that to belong to the group, we have to do like the others. Relationships between teenagers are more natural and spontaneous at this time [than in other age groups]. The friendships that are formed in adolescence are those that generally last a lifetime.”

Another upheaval: the adolescent changes in the eyes of adults. Because we change, because we grow up, we can no longer be, function or act as we used to. A distance, healthy although delicate to determine, allows us to reach a new social identity. Self-esteem is disturbed, as well as the emotional balance that prevailed in childhood. Friends and lovers take a more important part in our lives.

We readily define adolescence as a ‘crisis’. If there is a crisis, the stakes are huge at this pivotal time. It is up to the adults to whom the adolescent may confide to determine the ins and outs of the crisis in question, so as not to miss serious disorders or even the first signs of psychopathology – and on the other hand not to consider as ‘pathological’ adolescents who are just a little too flamboyant.

“Many mental illnesses can appear during adolescence, such as anxiety, depression, eating disorders, schizophrenia and psychotic disorders in general,” says Philippe Hercberg. Whether they take a restrictive or bulimic form, eating disorders, to which young women are particularly vulnerable, are actually the third most common chronic illness among adolescents.

“Someone who stops eating to lose a lot of weight, or who has repeated suicidal thoughts over time, a teenager who cuts himself off from the group and obviously a teenager who has hallucinations, this is not ‘normal’. And this even though anxiety disorders, depressive disorders and sleep disorders have exploded in the last couple of years. In all cases, it is the clinical interview that can determine if it is a pathology.”

Adolescence, then, is a decisive time – but a necessary stage to realise one’s self. A time, in short, to tame that inner panda, to learn the value of emotions and the importance of patience.

Turning Red is streaming on Disney+ from 11 March.

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