Heavy use of alcohol may slow the rate of growth in developing brains, according to a study conducted in monkeys.
The study, published in the journal eNeuro, shows that heavy alcohol use reduced the rate of brain growth by 0.25 millilitres per year for every gramme of alcohol consumed per kilogramme of body weight.
In human terms, that is the equivalent of four beers per day, said researchers from the Oregon Health and Science University in the US.
“Chronic alcohol self-intoxication reduced the growth rate of brain, cerebral white matter and subcortical thalamus,” researchers said in a statement.
They measured brain growth through magnetic resonance imaging of 71 rhesus macaques that voluntarily consumed ethanol or beverage alcohol.
The researchers precisely measured intake, diet, daily schedules and health care, thus ruling out other factors that tend to confound results in observational studies involving people.
The findings help validate previous research examining the effect of alcohol use on brain development in people.
“Human studies are based on self-reporting of underage drinkers,” said Christopher Kroenke, an associate professor at Oregon Health and Science University.
“Our measures pinpoint alcohol drinking with the impaired brain growth,” Kroenke.
The new study is the first to characterise normal brain growth of one millilitre per 1.87 years in rhesus macaques in late adolescence and early adulthood.
It further reveals a decrease in the volume of distinct brain areas due to voluntary consumption of ethanol.
Lead author Tatiana Shnitko, a research assistant professor at the Oregon Health and Science University, said previous research has shown the brain has a capacity to recover at least in part following the cessation of alcohol intake.
However, it is not clear whether there would be long-term effects on mental functions as the adolescent and young adult brain ends its growth phase, researchers said.