Teen Drinkers: The cognitive and structural impacts of drinking in adolescence
One demographic often underrepresented in scientific research about how alcohol affects our brain is that of adolescents. Whilst this is often due to a lack of data, given that many of them are underage drinkers, research is now making a concerted effort to understand how alcohol affects them specifically. With 25% of teens in Europe consuming alcohol by the age of 13[1] – and with much of this being binge drinking – the imperative for this kind of research is evident. One recent review highlighted adolescence as one of the three periods of our lives when we are most susceptible to the neurotoxic effects of alcohol.[2] This is because it is a crucial developmental period of the brain, with many synapses being pruned (the weak connections between neurones being severed) and increasing axonal myelination (boosting the speed of communication between neurones).[3] There is also some concern that any damage sustained through teenage drinking could persist into adulthood, thus increasing research in this area is very significant. We will examine the cognitive and structural impacts on the brain of drinking alcohol as an adolescent, and delve into some surrounding issues and concerns in the field.
Firstly, adolescence is understood to be a particularly vulnerable neurodevelopmental period – with many changes in the brain leading to volatile and risky behaviour. These changes involve a natural decline of grey matter, pruning away the weak synaptic connections formed during childhood. As well as this, the overall connectivity between brain regions is increased and the frontal lobe, which controls more advanced cognitive processes, begins to mature fully. Adolescents often succumb to alcohol not only because of surrounding social pressure to drink, but also the heightened reward sensitivity, impulsivity and diminished self-control to inhibit behaviours that accompany these changes in the brain.[4] One recent review even went as far as to claim that risky drinking was inevitable during adolescence.[5] The same review showed that a number of studies have found higher drinking in adolescence to be associated with poorer cognitive functioning overall. In other words, such functions as learning, psychomotor speed, attention, executive functioning and impulsivity were negatively impacted. And indeed, this kind of aberrant neural activity has been found during attentional, reward sensitivity and executive functioning tasks, in comparison to non-drinking adolescents.[6] Whilst the evidence seems clear and fairly damning, other researchers point out that these results are imperfect because of the confounding variable of other substances adolescents may have ingested. Indeed, many adolescent drinkers also have a pattern of cannabis use or other substances – meaning these impacts upon cognition may not exclusively be due to alcohol use.[7] Thus more research should attempt to find subjects who only consume alcohol and compare them to non-drinking adolescents, in order to further understand how cognition is impacted in the brains of drinking adolescents.
The cause of these cognitive deficits in the brains of adolescents is largely the result of structural damage as a result of drinking alcohol. As previously mentioned, underage drinkers are commonly excluded from sample data, but one very recent study focused on the brain structure changes in three groups of young people ranging from 9-29 years old. Data was obtained from the Dutch brain databases BrainScale and BrainTime, with brain scans from 2-3 different periods of each participant’s adolescence compared. The researchers found that drinking alcohol was associated with an accelerated decrease in grey matter volumes, particularly in the frontal and cingulate cortex areas. In other words, the volume of brain cells is reduced – a finding which is replicated in adults and problematic alcohol users later in life.[8] As well as this, alcohol was shown to lower the white matter integrity in these adolescents’ brains, meaning the connectivity between their brain cells was reduced. Notably, these effects were most consistent in older cohorts of adolescents, which is also when teenagers tend to drink the most. Another similar study which used population-based neuroimaging found that these effects were particularly heightened in the case of binge drinking – which is understood to be 4+ drinks for women and 5+ drinks for men in a short time period.[9] And over 20% of 15-19 year olds in European and other high income countries report that they binge drink at least occasionally.[10] Given also that brain maturation continues until the age of 25[11], these damaging structural effects of alcohol continue long past the time we might socially consider to be adolescence. However, it must be acknowledged that many of these findings are correlational; that is, as one increases, the other decreases. Not only this, but almost all of the studies with adolescents in this field rely on self-report to determine exactly how much they have drunk. This is even more subject to bias than adults, as underage drinkers may have extra incentive to conceal exactly how much they drink. Scientists are now suggesting the possibility of a wearable device or smartphone monitoring to more accurately measure how much adolescents are drinking, combined with the unshakeable biological markers of urine, spit or blood, for example. The most scientifically robust conclusion would need to find a causal relationship – i.e. by creating a group of drinking teenagers and seeing the resulting structural impacts on their brain, compared to a group of non-drinking teenagers. As this would be a highly unethical method, this field also relies on animal studies to show us how alcohol impacts the brain structure of adolescents.
Animal studies in rodents and non-human primates have replicated the findings that cognition is negatively impacted when adolescents drink heavily during this period of significant brain development.[12] However, the conclusions are stronger because researchers were able to precisely monitor and control the alcohol intake over the course of these animals’ lives. Because of this, they were able to find that many of these same cognitive detriments actually persist into adulthood. Very novel findings even suggest the structural damage caused by alcohol may even interrupt the normal process of the brain’s reward systems – the dopamine circuits – which could lead to a higher responsivity to alcohol in adulthood. This would simply be another positive feedback mechanism of addiction, acting to pull people into problematic alcohol behaviours later in their life. Another facet of this area currently under research is the possibility that some adolescents have some pre-existing neurobiological vulnerabilities, before they even begin to drink.[13] This means they experience more impactful and detrimental cognitive and structural effects when drinking alcohol. However, it is currently very difficult to extricate what is due to these pre-existing vulnerabilities, or simply just the typical neurological damage caused by adolescent alcohol overuse – more longitudinal studies are needed to pull apart these factors. The research of how alcohol affects the brain structure and cognition of adolescents is thus very useful to understand some of the roots of later problematic alcohol use, and move towards developing more effective forms of early intervention.
The changing neurobiology of the brain of adolescents, combined with their social contexts of binge drinking and peer pressure, creates the perfect recipe for them to overconsume alcohol during their teen years. This does result in changes to the grey and white matter of their brains, with some damage seeming to persist into adulthood with consequences for later drinking behaviour. Cognition is negatively impacted by these structural changes, leading to notable reductions in a range of attentional, functional and behavioural tasks. Research is currently focusing on early signs that an individual may be more susceptible to the neurotoxic effects of alcohol, as well as formulating more effective early intervention strategies to prevent issues with alcohol in adulthood.
References
[1] World Health Organization. (2018) Adolescent alcohol-related behaviours: trends and inequalities in the WHO European Region, 2002–2014.
[2] Mewton, L., Lees, B., Rao, R.T. (2020) Lifetime perspective on alcohol and brain health. BMJ. 371. Available at: https://www.bmj.com/content/bmj/371/bmj.m4691.full.pdf
[3] Spear, L.P. (2018) Effects of adolescent alcohol consumption on the brain and behaviour. Nat Rev Neurosci. 19. 197-214.
[4] Romer, D,. Reyna, V.F., Satterthwaite, T.D. (2017) Beyond stereotypes of adolescent risk taking: Placing the adolescent brain in developmental context. Dev Cogn Neurosci. 27. 19–34.
[5] Lees, B., Meredith, L.R., Kirkland, A.E., Bryant, B.E., Squeglia, L.M. (2020) Effect of alcohol use on the adolescent brain and behavior. Pharmacol Biochem Behav. 192. 172906.
[6] Lees, B., Meredith, L.R., Kirkland, A.E., Bryant, B.E., Squeglia, L.M. (2020) Effect of alcohol use on the adolescent brain and behavior. Pharmacol Biochem Behav. 192. 172906.
[7] Ibid.
[8] Yang, X. et al. (2016) Cortical and subcortical gray matter shrinkage in alcohol-use disorders: A voxel-based meta-analysis. Neurosci. Biobehav Rev. 66, 92–103.
[9] Topiwala, A., Ebmeier, K.P, Maullin-Sapey, T., Nichols, T.E. (2022) Alcohol consumption and MRI markers of brain structure and function: Cohort study of 25,378 UK Biobank participants. NeuroImage: Clinical. 35. 103066.
[10] World Health Organization. (2018) Global status report on alcohol and health 2018. WHO.
[11] Giedd, J.N. (2008) The teen brain: insights from neuroimaging. The Journal of Adolescent Health: Official Publication of the Society for Adolescent Medicine. 42(4). 335–43.
[12] Lees, B., Meredith, L.R., Kirkland, A.E., Bryant, B.E., Squeglia, L.M. (2020) Effect of alcohol use on the adolescent brain and behavior. Pharmacol Biochem Behav. 192. 172906.
[13] Ibid.