A study of primates showed that the equivalent of four drinks a day over a one-year period had dramatic effects on brain growth in adolescence. Although it is excessive consumption, this study shows the risks of alcohol on developing brains.
Previous studies in adolescents have shown that there is a link between excessive alcohol consumption and changes in brain development.
However, they used self-reported data and the ambiguous legal framework of these consumptions did not allow researchers to obtain reliable and accurate data on the effects of alcohol on brain development.
An American team, however, has managed to fill these gaps by observing these effects during adolescence in our closest cousins: primates.
The risks posed by excessive alcohol consumption and the dangers of developing alcohol dependence are widely known by the population. Other more devious problems, such as its link with the development of certain cancers, are increasingly well documented in the scientific literature.
Alcohol consumption has particularly dramatic effects on the brain, especially during adolescence. Now, this period is exactly the time when one begins to be exposed to alcohol.
A critical period
During adolescence, the brain goes through several stages of transformation that will continue until the age of 25 years. This is because at birth our brain contains many more neurons than we need.
With the years, all these neurons, called the gray matter, will be pruned, that is to say that the most activated will be maintained, while others, obsolete, will be eliminated.
This leads to a decrease in the volume of gray matter, while increasing the efficiency of the remaining cells.
Conversely, during the same period, the number of connections between these neurons increases. The long filaments that connect the neurons to each other, the axons, are covered with a fatty insulating substance called myelin, which helps protect the nerve signal that passes through them.
As a whole, this mass is called white matter, and its volume increases from adolescence to adulthood.
Magnetic resonance imaging in adolescents has shown that this process is impaired in heavy alcohol users, resulting in a faster decrease in gray matter and a smaller increase in white matter.
The new study in a cohort of 71 rhesus monkeys confirmed these consequences on brain development. Controlled conditions during this experiment allowed to evaluate the damage with much more precision.
In terms of increased brain volume, researchers first estimated that monkeys increased by about 0.54 milliliters each year during adolescence.
This same growth decreased by 0.25 milliliters per year for every gram of alcohol consumed per kilogram of body weight. In an average human being, this figure equals four drinks a day.
Although researchers have observed that there is still white matter growth among animals in the heavy drinkers group, the heavy drinker group was significantly reduced, from an annual increase of 4.7% to an increase of 2.6%.
In addition, some areas of the brain with a significant role in addictive behaviors, such as the thalamus, also saw their growth decline in heavy drinkers from an annual increase of 5% to 1.8%.
These results show not only the negative influence of alcohol on brain development, but also the possibility that it promotes addictive behaviors later in life. Researchers now have to check whether this decrease is responsible for cognitive problems during adulthood.
Although the study did not take into account the genetic or social factors associated with excessive alcohol consumption, the researchers’ conclusions are similar to those of studies already done on humans or mice.
As our second lead editor, Fiona Johnson provides guidance on the stories Teslabel reporters cover. She has been instrumental in making sure the content on the site is clear and accurate for our readers. If you see a particularly clever title, you can likely thank Fiona. Fiona received a BA and and MA from Fordham University.