Heavy alcohol use inhibits, damages brain growth, studies find

Heavy use of alcohol among adolescents and young adults is not only dangerous in its own right, but new research in nonhuman primates shows that it can actually slow the rate of growth in developing brains.

The study, published in the journal eNeuro, showed that heavy alcohol use reduced the rate of brain growth by 0.25 milliliters per year for every gram of alcohol consumed per kilogramme of body weight. In human terms, that’s the equivalent of four beers per day. The research involved rhesus macaque monkeys at the Oregon National Primate Research Center, United States.

“Chronic alcohol self-intoxication reduced the growth rate of brain, cerebral white matter and subcortical thalamus,” the researchers write.

Researchers measured brain growth through magnetic resonance imaging of 71 rhesus macaques that voluntarily consumed ethanol or beverage alcohol.

Scientists 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 in the study help validate previous research examining the effect of alcohol use on brain development in people.

The new study is the first to characterize normal brain growth of 1 milliliter per 1.87 years in rhesus macaques in late adolescence and early adulthood. And it further reveals a decrease in the volume of distinct brain areas due to voluntary consumption of ethanol.

Meanwhile, the myth that one or two drinks a day could protect against stroke has finally been debunked by scientists.

Researchers at the University of Oxford said that alcohol not only does not have a protective effect, but even moderate drinking raises the risk by up to 15 per cent.

Previous studies have suggested that one or two glasses of wine or beer a day could lower the risk of stoke by more than 50 per cent, and seemed to show that people who abstained from alcohol were in greater danger than moderate drinkers.

But the scientists said those studies had been skewed by people who had given up alcohol because of underlying health problems. So they were at greater risk not because they were not drinking.

Also, although the harmful effects of alcohol on the brain are widely known, the structural changes observed are very heterogeneous. In addition, diagnostic markers are lacking to characterize brain damage induced by alcohol, especially at the beginning of abstinence, a critical period due to the high rate of relapse that it presents.

Now, a joint work of the Institute of Neuroscience CSIC-UMH, in Alicante, and the Central Institute of Mental Health of Mannheim, in Germany, has detected, by means of magnetic resonance, how the damage in the brain continues during the first weeks of abstinence, although the consumption of alcohol ceases.

The research, published in JAMA Psychiatry, whose first author is Silvia de Santis, shows that six weeks after stopping drinking there are still changes in the white matter of the brain, as revealed by the neuroimaging study carried out on ninety voluntary patients interned for his rehabilitation treatment in a German hospital.

The results of this work are surprising, explains Dr. Santiago Canals, of the Institute of Neurosciences CSIC-UMH, who has coordinated the research: “Until now, nobody could believe that in the absence of alcohol the damage in the brain would progress”.

Ninety patients with an average age of 46 years hospitalized because of an alcohol use disorder participated in this study. To compare the brain magnetic resonances of these patients, a control group without alcohol problems was used, consisting of 36 men with an average age of 41 years.

“An important aspect of the work is that the group of patients participating in our research are hospitalized in a detoxification program, and their consumption of addictive substances is controlled, which guarantees that they are not drinking any alcohol. Therefore, the abstinence phase can be followed closely”, highlights Dr. Canals.

Another differential characteristic of this study is that it has been carried out in parallel in a model with Marchigian Sardinian rats with preference for alcohol, which allows to monitor the transition from normal to alcohol dependence in the brain, a process that is not possible to see in humans”, explains Dr. De Santis.

The damages observed during the period of abstinence affect mainly the right hemisphere and the frontal area of the brain and reject the conventional idea that the microstructural alterations begin to revert to normal values immediately after abandoning the consumption of alcohol.

With the consumption of alcohol “there is a generalized change in the white matter, that is, in the set of fibers that communicate different parts of the brain. The alterations are more intense in the corpus callosum and the fimbria.

The corpus callosum is related to the communication between both hemispheres. The fimbria contains the nerve fibers that communicate the hippocampus, a fundamental structure for the formation of memories, the nucleus accumbens and the prefrontal cortex, “explains Dr. Canals. The nucleus accumbens is part of the reward system of the brain and the prefrontal cortex is fundamental in decision making.

The researchers from Alicante and Germany now try to characterize the inflammatory and degenerative processes independently and more precisely, in order to investigate the progression during the early abstinence phase in people with alcohol abuse problems.