Author: Sarah-Jayne Blakemore
By shining a long overdue light on adolescence, this book skilfully demystifies what appears to be a pivotal but eccentric stage in the human journey from childhood to adulthood. With a most enlightening narrative, the author unravels the biological drivers of the peculiar behaviours that characterise the teenage years – a volatile period during which she said ‘the brain is changing in important ways’. The author argues stridently that this phase is ‘central to human experience‘, being the critical time when teenagers are preparing to become ‘individual and social human beings’. In an approach that correlates the observable behaviours of adolescence, to the accompanying brain developmental changes, the book attributes the passion and creativity of the juvenile years to the malleability of the brain’s neural pathways. The author’s key message is undoubtedly her advocacy for a better appreciation and understanding of teenage behaviour; by highlighting the rapidly evolving anatomical, clinical, and imaging features of adolescence, and by demonstrating that ‘the teenage brain isn’t broken‘, she urges that ‘we should understand it, nurture it – and celebrate it’ (pages 202, 2 and 6-7).
The critical transformations taking place in the adolescent brain formed the major theme of the book. This discussion focused on the importance of the adolescent years in the emergence of the ‘sense of self‘ – what the author defined as the ‘looking glass self‘ by which people comprehend ‘who they are’ and how others see them. The author explained that the generation of the sense of self is symbolised by the development of introspection or metacognition, the mechanism by which people acquire insights into their ‘emotions and thought processes’. Other consequential adolescent transitions the book explored are the development of ‘a more complex sense of morality‘, and the awareness of ‘the political realities of society’. The book also discussed how adolescent peculiarities such as sensation-seeking and self-consciousness are mirrored by brain imaging changes. For example, it pointed out that teenage embarrassment is accompanied by an increase in brain imaging activity in the medial prefrontal cortex – ‘a key region of the “social brain” that is involved in reflecting on the self’ (pages 19, 24-28 and 3-6).
The concept of synaptic pruning was at the heart of the book’s exploration of the brain processes that drive adolescent behaviour. The author explained that the formation of synapses, the junctions between neurones, rapidly accelerates after birth with the result that many brain areas accommodate synapses ‘far in excess of what the brain will ever need’. Referring to synaptic pruning as the brain’s mechanism of preventing this excessive synaptogenesis, the author explained that it ‘fine tunes brain tissue so that it is most efficiently suited to the circumstances in which the child is growing up’. The author specifically pointed out that synaptic pruning is proof of the considerable role the environment plays in the acquisition of behavioural skills such as impulse control, and of cognitive abilities such as non-verbal reasoning and mentalizing, the latter being the ability to appreciate ‘other people’s perspectives‘. Because these skills are acquired in adolescence, the author advised that they should not be actively taught before this phase of life (pages 60-64, 111-118 and 91-94).
Risk-taking, as expected, is a major theme of the book, and the author explored its diverse facets – from smoking and binge-drinking to dangerous driving and unsafe sex. She vividly described the hold that hazardous activities have on teenagers, and she partly attributed this to the ‘developmental mismatch‘ that exists between the earlier maturation of the limbic system which regulates emotions, and the later development of the prefrontal cortex which controls introspection. This ‘dual systems model‘, the author argued, is why ‘adolescents get a kick out of taking risks’, and why they are often unable ‘to stop themselves doing so in the heat of the moment‘. The book however also implicated peer pressure in teenage risk-taking, asserting that ‘most adolescents who take…risks do so when they are with friends‘. The author explained that peer pressure has such a strong influence on adolescents because of their strong need for ‘social acceptance‘, and because of their tendency to judge their self-worth by what their friends think about them. The author however stressed that there are evolutionary benefits for the preference adolescents show for their friends over their parents, arguing that this independence is crucial ‘if they are to thrive later in life’ (pages 31-41, 73-74 and 133-144).
Even though the book’s focus was the adolescent period, the author also presented a helpful comparative assessment of brain development in neonates and younger children. For example, the author noted that newborn babies have a ‘very primitive‘ sense of self, but by 18 months, using the mirror self-recognition test, they show ‘advanced signs of an understanding that they exist as individuals‘. She also showed that at this age, babies can ‘differentiate between their own feelings and those of others’, and appreciate that ‘different people have different emotions and desires‘. Other remarkable landmarks highlighted by the author are the ability of neonates, on the day of their birth, to ‘distinguish between male and female voices’, and within a few days, to recognise the faces and voices of their mothers. Charting their development further, some of which were identified by the ingenious Sally-Anne task, she noted that babies ‘begin to communicate both verbally and non-verbally’ by the age of 2 years, and to express their beliefs by the age of 4 or 5 years (pages 20-21 and 100-108).
The subject that perhaps best resonates with clinical medicine is the recognition that some mental health disorders have a predilection for the adolescent period. For example, the author cited studies which showed that ‘three-quarters of all cases of mental illness…start at some point before the age of 24‘, and she illustrated this with the example of schizophrenia which she said almost consistently begins in the teenage years. The book referred to schizophrenia as a developmental disorder that probably results from exaggerated adolescent synaptic pruning, and as the failure of ‘the mechanism for distinguishing what the world does to you and what you do to yourself‘. The book also reviewed how new discoveries, such as the ‘greater decline in grey matter‘ of the brains of adolescents who are at risk of developing schizophrenia, are helping to enhance our understanding of mental disorders. Other psychiatric problems the book explored included depression, and the effects of cannabis and alcohol on the adolescent brain (pages 11-12, 157-159 and 163-175).
This book about adolescence does more than give an insight into the brain changes occurring at this time; it also provides a panoramic view of development from childhood to early adulthood. With simple prose and appropriate personal anecdotes, the author projected the key themes of her book effectively, noting the significant social, clinical, and public health dimensions of adolescence. As she corrected the misconceptions that surround teenage behaviours, she also argued for a better appreciation of the important transformations that are occurring at this time. Whilst the tendency of the book to cite multiple studies to support each theme appears occasionally excessive, this does not detract from the smooth flow of the narrative, nor does it impair the key objectives the book set out to achieve.
This book is a broad sweep of development from infancy to early adulthood, and it is as comprehensive as it is enlightening. It stresses the importance of an enigmatic stage of life that is as perplexing to adolescents as it is to those who interact with them. By establishing the sources of, and the justifications for, adolescent behaviour, society as a whole is better able to address adolescent issues more sensitively and effectively. The book also provided invaluable guides for the best public health approaches to adolescents issues, and these take into account their biological and social circumstances. The book is an important contribution to the understanding of an important phase of human development, a subject at the heart of healthcare, and I recommend it to all doctors.
Publisher, Place, Year: Transworld Publishers, London, 2018
Number of chapters: 12
Number of pages: 240
Star rating: 5