Analysis: some remarkable biological and psychological changes occur during adolescence which explain how teenagers behave

Adolescence can be a tough time to live through for teenagers – and their parents. Seemingly overnight, children who were sweet and good-natured transform into grunting, rebellious, eye-rolling creatures. However, a lot of stereotypical teenage behaviour can be explained by understanding the changes which occur in the brain and body as we develop from child to adult.

From BBC, Kevin becomes a teenager

Physical changes

Most parents of teenagers will have at some point explained the erratic behaviour of their offspring with the word "hormones". However, this simple word does not do justice to the complicated series of biological changes that occurs during puberty. From around the age of 8, a chemical called gonadotrophin releasing hormone (GnRH) starts to get released from a region of the brain called the hypothalamus. GnRH in turn signals the pituitary gland at the base of the brain to release Follicle Stimulating Hormone (FSH) and Luteinizing Hormone (LH) into the bloodstream.

In boys, these hormones reach the testicles and initiate the production of sperm and testosterone. In girls, it is the ovaries that are acted upon to start producing eggs and oestrogen. The increased testosterone in males promotes skeletal growth, increases muscle mass and deepens the voice. In females, the increased oestrogen levels encourages fat production in the breast and hips, and leads to the onset of menstruation.

Teenagers experience mood swings and may struggle to recognise emotions in others, leading to accusations of selfishness

Adrenal glands in both sexes release androgens; hormones which encourage hair growth, particularly in the pubic and armpit regions. Naturally, this cocktail of hormones also leads to increased sexual interest. Unfortunately, just when a teenager might want to appear attractive to others, the adrenal androgens also stimulate extra oil production in the skin, which can clog hair follicles, leading to the dreaded development of spots. These complex, but very normal, processes continue throughout puberty, but the changes they cause in the developing teenage body can mean a highly emotional time for those experiencing it.

Mental changes

From Greater Good Science Center, author and neuropsychiatrist Daniel Siegel on how adolescence remodels the brain and increases a willingness to take risks

Scientists used to think that most important brain development occurred in childhood. However, a large body of evidence over the last 20 years now reveals that the teenage brain also undergoes several remarkable changes. In particular, neuro-imaging studies show that the cells in the pre-frontal cortex region undergo substantial rearrangement as a child moves toward adolescence. 

During this period, weakly established neuronal interactions get discarded, while well-used connections get preserved and strengthened. This process of synaptic pruning has been likened to the pruning of a rose bush; cutting back to ensure better growth in future. However, the pre-frontal cortex is the part of the brain that is responsible for decision-making, planning, self-control, self-awareness and social interaction, so these cognitive abilities are deeply affected in teenagers during this period of brain reorganisation.  

As a result, teenagers experience mood swings and may struggle to recognise emotions in others, leading to accusations of selfishness. Impaired memory and reduced organisational capacity contributes to the educational dip suffered by many teenagers starting secondary school, when a previously good pupil starts to struggle with schoolwork. And it is not surprising that this period of brain restructuring is linked with the appearance of mental health problems in some teenagers, although this is also influenced by external environmental factors.

From RTÉ Radio 1's Sunday Miscellany, Kate Kerrigan's Teenage Kicks on the eternal teenager within

This rewiring of the brain also explain the tendency of teenagers to make irrational, impulsive decisions. Sensation-seeking and risk-taking is characteristic of teenage life and this is related to the function of dopamine, a neurotransmitter which determines how much we enjoy an experience.

Dopamine levels are somewhat lower in teens than in children and adults, which partly explains why they always claim to be bored. However, their response to dopamine when it is produced is much more sensitive, so although more stimulation is needed to release dopamine, there is a greater satisfaction when it is. Hence, trying new things to get teenage kicks is entirely normal, driven by the human need to satisfy that internal reward system. Unfortunately, this sensitised reward system in the brain, coupled with diminished self-control, also means teenagers are particularly susceptible to addiction when experimenting with exciting new experiences.

Behavioural changes

A key contributory factor to teenage behaviour is peer pressure and many studies have identified the need to "fit in" as a crucial element of social development at this age. Building social skills means it is very important that a teenager’s evolving identity is acceptable to others. But that means most teenagers will have to endure that intensely awkward period of self-consciousness when they care deeply about what other people think of them. Conforming to the latest trends and copying others, especially in early adolescence, is one way to fit in and minimise the chance of social isolation.

The need for social acceptance also influences risk-taking behaviour and impressing your peers becomes more important than making the "right" decision. For example, one study used a driving simulation game to show that teenagers surrounded by friends were much more likely to drive dangerously than when playing alone, whereas adults showed little change. Parents often declare that they don’t care what their teenager’s friends are doing, but studies like this prove that the teenager cares very much indeed!

From RTÉ Archives, an episode of Family Matters looks at teenage bedrooms

Finally, parents will often despair at the sleeping routine of their teenage children. However, research has shown that natural fluctuations in levels of melatonin, a hormone which determines our sleep patterns, is very different in teenagers compared to children and adults. As a result, the sleep-wake cycle of teenagers shifts so that they are more awake late at night, but sleepier in the morning. It means that they are effectively jet-lagged most of the time during a school week, so those long weekend lie-ins are simply the body’s attempt to catch up on much-needed sleep.

So whether you are a teenager or a parent of one, the key to surviving those turbulent adolescent years is appreciating that it is all a perfectly normal process of physical, mental and social development. And, like, OMG, I'm not even joking about that, K?

As part of the Northern Ireland Science Festival 2020, Declan McKenna will be presenting Angst & Adolescence: The Science of Teenagers at the Nerve Centre, Derry (tonight) and the Crescent Arts Centre, Belfast (Wednesday). 


The views expressed here are those of the author and do not represent or reflect the views of RTÉ