Adolescents should not be expected to fully think and behave like adults, as they are still in flux and ‘becoming’. Key differences include the ability to weigh outcomes outside of ones’ direct experience, reactivity to potential rewards, tolerance for uncertainty and the ability to assess the value of an outcome and risks associated with it (Hartley and Somerville, 2015).
Dynamic changes in brain structure, function and neuromodulatory systems begin at the onset of puberty and continue throughout adolescence. The overall size of the brain does not significantly change, but substantial anatomical reorganisation happens at the microscopic, neural cell level. A new, rapid process of synaptic pruning and connective reorganisation begins in the second decade of life and continues for ten years or more. The prefrontal cortical, striatal, and salience processing networks undergo significant changes in connectivity. This process can be visualised with functional MRI (Somerville et al., 2013). As these structural changes occur, they dynamically constrain and amplify key components in decision-making. Thus, many critical aspects of complex decision-making in adolescence are configured differently to those in adults. It is as if the brain is being ‘rewired’, and is in a prolonged transition between child and adult states. Adolescents should not be expected to fully think and behave like adults, as they are still in flux and ‘becoming’. Key differences include the ability to weigh outcomes outside of ones’ direct experience, reactivity to potential rewards, tolerance for uncertainty and the ability to assess the value of an outcome and risks associated with it (Hartley and Somerville, 2015).
From early childhood, individuals start to learn how to make good decisions by observing and experiencing the positive and negative consequences of their actions. When making decisions, children tend to evaluate their options solely on the basis of their immediate and previous experiences. Adults generally take into account the environment and consider numerous potential outcomes outside of their direct personal experience including waiting for benefits (‘delayed gratification’). This process requires contributions from the prefrontal and hippocampal regions, pathways that begin to be strengthened during adolescence. The ability to incorporate applied, indirect knowledge into decision-making begins to emerge in adolescence and continues to develop well into adulthood (Hartley and Somerville, 2015).
Life experience and increased knowledge of the world are but two of the factors that aid decision-making. Adults also rely on their prefrontal cortex to give them a full awareness of the long-term consequences of their decisions. The neuronal architecture required for complex decision-making, particularly decisions that may impact on their medium to long-term future, is not fully developed in teenagers. Because corticostriatal connectivity is still under construction, adolescents tend to prioritise feelings over facts when it comes to decision-making (Campellone and Turley, no date).
Adolescents also assess risk in different ways to adults. They struggle to accurately value an outcome that may be in the future, particularly if it is outside of their experience of life to date. In a situation where immediate and direct consequences will occur as a result of their decisions, teenagers are more likely to ignore their explicit knowledge of the probability of a negative outcome and are more willing to take risks to obtain the potential rewards on offer (van Duijvenvoorde et al., 2015). They are also more tolerant of uncertainty with respect to the outcomes associated with their decisions. In other words, adolescents are more likely than adults to agree to a course of action associated with an unknown, or unquantified outcome, allowing them to explore and be open to new experiences.
Peer influence is another powerful factor that disproportionately impacts decision-making during the teenage years. Adolescence is a period of life in which peer relationships become increasingly important. This appears to be ‘hard wired’ in biology, maybe as part of a move beyond initial caregivers’ and parental approval and influence, in order to learn more social rules of the collective alongside individual independence. Being observed by a peer is sufficient to induce high levels of physiological arousal in adolescents and modulation of the corticostriatal valuation systems (Somerville, 2013; Somerville et al., 2013; Knoll et al., 2015). For early adolescents, the opinions of other teenagers about risk matter more than the opinions of adults (Somerville et al., 2013; Knoll et al., 2015).
Thus there is a large body of neuropsychological literature that describes the systematic ways in which the decision-making processes of teenagers and adolescents differ from those of both younger children and adults. These systematic differences are underpinned by the significant structural reorganisation that the brain undergoes in the second and third decades of life. The implications of this literature are increasingly recognised in the criminal justice systems in the UK and the USA (Hacker and Baranoski, 2017; Law Society of Scotland, 2020). This literature also has a direct bearing on the ability of teenagers to weigh and consider information for elective, non-essential, healthcare interventions.
The ability of a young person to provide consent for any elective medical or surgical intervention cannot entirely be considered ‘a moot point’ as has been argued by some (The Lancet Child Adolescent Health, 2021). Whilst parental consent may be required prior to the commencement of any drug for young children, it is the adolescent’s desire to undergo medical interventions that is both the starting point and driving force behind this decision with respect to transition. This desire is based upon the teenager’s understanding of the risks and benefits of the intervention they are seeking and/or being offered.
In this are of medicine, the evidence base ought to be robust to support decision-making, as for any other clinical area. As described above, an adolescent’s understanding will inevitably be constrained by neurobiological factors. It is crucial to consider the neurobiological and neuropsychological constraints on the decisions that can be made by any teenager considering treatment that will result in lifelong and irreversible changes to their body, such as medical and surgical interventions for gender dysphoria. Younger teenagers will not have the cognitive architecture necessary to give truly informed consent to such procedures. Nor can adolescents have the necessary life experience to understand the implication of a damaged sex life (from stopping physical maturity or ablative operations), when they cannot know first hand what it is that they are alienating. Neuroscience has much to inform clinicians about the adolescent brain and the way in which teenagers understand the world and make decisions. This knowledge must be integrated into the provision of any medical treatments that may have a long term and irrevocable impact on their lives as adults.
Campellone, J. and Turley, R. K. (no date) Understanding the Teen Brain, University of Rochester Medical Center Encyclopaedia. Available at: https://www.urmc.rochester.edu/encyclopedia/content.aspx?ContentTypeID=1&ContentID=3051
van Duijvenvoorde, A. C. K. et al. (2015) ‘Neural Correlates of Expected Risks and Returns in Risky Choice across Development’, Journal of Neuroscience, 35(4), pp. 1549–1560. doi: 10.1523/JNEUROSCI.1924-14.2015.
Hacker, R. and Baranoski, M. (2017) ‘Impact of Neuroscience and Evolving Standards of Decency on Juvenile Sentencing’, Journal of the American Academy of Psychiatry and the Law, 45(1), pp. 107–109. Available at: http://jaapl.org/content/45/1/107.
Hartley, C. A. and Somerville, L. H. (2015) ‘The neuroscience of adolescent decision-making’, Current Opinion in Behavioral Sciences, 5, pp. 108–115. doi: 10.1016/j.cobeha.2015.09.004.
Knoll, L. J. et al. (2015) ‘Social Influence on Risk Perception During Adolescence’, Psychological Science, 26(5), pp. 583–592. doi: 10.1177/0956797615569578.
Law Society of Scotland (2020) Brain not fully developed until age 25, research reveals, Lawscot.org.uk. Available at: https://www.lawscot.org.uk/news-and-events/legal-news/brain-not-fully-developed-until-age-25-research-reveals/.
Somerville, L. H. et al. (2013) ‘The Medial Prefrontal Cortex and the Emergence of Self-Conscious Emotion in Adolescence’, Psychological Science, 24(8), pp. 1554–1562. doi: 10.1177/0956797613475633.
Somerville, L. H. (2013) ‘The Teenage Brain’, Current Directions in Psychological Science, 22(2), pp. 121–127. doi: 10.1177/0963721413476512.
The Lancet Child Adolescent Health (2021). ‘A flawed agenda for trans youth’, Lancet Child Adolesc Health, 5(6):385. doi: 10.1016/S2352-4642(21)00139-5.