Monkeys Who Drank Alcohol During Adolescence Had Slower Brain Growth Than Their Peers, Study Finds

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Drinking alcohol during adolescence could slow brain development, according to scientists who studied monkeys.

As we mature from adolescence to adulthood, our brains enter the last stages of development. This is also the time when some individuals start to binge drink. A 2017 survey, found, for example, that around 14 percent of high school students in the U.S. binge drank in the past 30 days, and more than 4,300 underage drinkers died each year, according to the Centers for Disease Control and Prevention. And underage drinkers are more likely to consume more alcohol in one sitting than those above the age of 21. This behavior exposes young people to the harms of alcohol, including memory lapses, and changes in brain development, the agency warned.

The authors of a paper published in the journal eNeuro wanted to explore the effect alcohol may have on the teenage brain.

To find out more, the team studied 71 rhesus macaque monkeys at the Oregon National Primate Research Center. The researchers gave the animals unrestricted access to ethanol alcohol and water for 22 hours per day. The team used magnetic resonance imaging to study the brains of the monkeys at the start of the study before they had consumed alcohol, and at around 6 and 12 months in. They also took samples of the animals' blood.

The results revealed that the monkeys who drank heavily, or the equivalent of around four beers per day, saw their brain growth reduced by 0.25ml per year for every gram of alcohol consumed per kilogram of body weight. Drinking regularly cut the growth of cerebral white matter, and the subcortical thalamus, which plays a role in shooting off motor and sensory signals.

The team hopes its work will prompt future research into whether these changes occur in teenage humans, and whether they make a person more vulnerable to having drinking problems later in life.

Christopher D. Kroenke, co-author of the study at the Oregon Health and Science University Advanced Imaging Research Center told Newsweek: "This research affirms that alcohol drinking that begins in late adolescence or young adulthood can interfere with normal brain development.

"It has been known for a long time that alcohol reduces brain size in chronic alcoholics. Our study provides evidence that drinking alcohol by itself slows the rate of brain growth, in the absence of confounding factors such as other drug use, nutritional factors, etc.

"In our study, we begin to unravel how various brain regions respond differently to daily alcohol drinking. This information may help us learn which brain cells, circuitry, or developmental processes are specifically altered by the presence of alcohol. This level of detail can be critical for prevention or intervention strategies to mitigate alcohol-induced damage."

However, Kroenke said that while the researchers had been gathering data on the project for 12 years in male subjects, fewer females had been studied, and so the authors can't be sure of the potential differences between sexes.

Tatiana Shnitko, lead author and research assistant professor in the Division of Neuroscience at Oregon National Primate Research Center, commented on the potential harms of adolescent drinking a statement. She said: "This is the age range when the brain is being fine-tuned to fit adult responsibilities. The question is, does alcohol exposure during this age range alter the lifetime learning ability of individuals?"

Last year, a separate study published in the journal Alcohol concluded that drinking alcohol as a teenager could negatively affect an individual's metabolism.

Researchers found even drinking in moderation could have a negative affect on how the body generates energy. The work built on a previous study by the same team at the University of Eastern Finland, which suggested drinking can reduce gray matter volume in the brains of teens, leading the team to believe the two may be linked.

Noora Heikkinen, a researcher at the University of Eastern Finland's Institute of Clinical Medicine, told Newsweek at the time: "Despite [the participants'] alcohol use being 'normal,' their metabonomic profile and brain gray matter volumes differed from those in the light-drinking participant group." This raises the question of whether there is a safe limit for drinking, she argued.