Adolescent and Brain Development

Brain development occurs throughout adolescence and into early adulthood (1), however changes in adolescent brain development are more subtle compared to early infant and childhood brain development (2). Adolescent brain development involves a reduction in gray and white matter volumes (3) as the brain specialises to reflect the individual's environment and experiences (4, 5). This remodelling and refinement of the brain also reflects the social, physiological and psychological development of adolescents (6), for example, in the increased cognitive skills and in emotional processing (6) that occur during this phase of development.

There are very few human studies that provide definitive information about the effect of alcohol on adolescent brain development (1, 7). This is partially due to tight ethical controls on such studies (7). Existing human studies report that binge drinking (four or more drinks per occasion) in adolescence can cause short term memory problems, most often in spatial working memory tasks (1) or recording information about the spatial orientation of the environment. Human studies also provide evidence that alcohol affects adolescents differently to adults with adolescents more vulnerable to the impact of alcohol on brain function and behaviour (1). This may, in part, be explained by adolescents' limited experience in drinking situations and limited capacity to predict factors that will impact on the drinking event. Young people also have lower tolerance to the effects of alcohol, which makes the loss of function more immediate (8).

While animal studies report mixed findings, they are useful for comparison with humans as amount and frequency of drinking can be tightly controlled. For example, animal studies report that binge drinking adolescent animals show greater memory deficits than binge drinking adult animals (9, 10) and after repeated high levels of adolescent alcohol exposure some of these deficits continue into adulthood (11, 12). Conversely, binge drinking adult animals are less able to perform in non-stressful spatial memory tasks (13), and are more vulnerable to the acute effects of alcohol, such as alcohol-induced sedation (14) and motor impairments, (15) than adolescent alcohol-exposed animals. There is evidence that binge alcohol consumption in animals causes alterations to specific brain receptors (16) and molecular networks (17), however the impact that this has on critical functioning is less clear.

When results from animal and human studies are combined it seems that excessive alcohol consumption may have an impact on short term memory and on brain function that underlies memory formation (1). However, it is unclear if excessive alcohol consumption causes these problems or if there are underlying factors, which pre-date the onset of regular binge-level alcohol intake, that impact on the development of future problems (6). Longitudinal studies are necessary to provide clarity to our understanding in this area (6). Other possible consequences of a one-off, or more regular, excessive alcohol use occasions on the adolescent brain also requires further study, as there are few studies that provide conclusive information. The impact of low level use of alcohol (or in fact any level under four drinks per occasion) also remains undefined.

Intuitively, it seems likely that excessive alcohol consumption will have an impact on adolescent brain development, however, to date, research studies fail to provide a definitive answer.

Note: Janette Smith, an Australian researcher at the National Drug and Alcohol Research Centre (NDARC), provided peer review for this summary. Janette is researching the impact of alcohol on adolescent executive functioning (planning, working memory, attention, problem solving, verbal reasoning, inhibitions, mental flexibility, multi-tasking, initiation and monitoring of actions) and the results of this study are expected in late 2014.


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