Deep in your brain, there’s a very important tissue called white matter. Only in the past decade have scientists realized white matter isn’t passive infrastructure but in fact a heap of nerve fibers that affect learning and brain function. Importantly, scientists recently discovered that alcohol detrimentally affects white matter, even after a person has quit drinking, reporting their news on Tuesday in JAMA Psychiatry.

Previous studies have shown that alcohol changes the structure of white matter for the worse, even if a person is only drinking moderate amounts, which can lead to accelerated cognitive decline as a person gets older. This new study is unique in that it is one of the first to examine the state of white matter after a person becomes sober. And the outlook is not great.

Lead author Santiago Canals, Ph.D., a principal investigator at the Institute of Neurosciences in Spain, announced Tuesday that until now, “nobody could believe that in the absence of alcohol the damage in the brain would progress.”

Micro-structural changes in brain white matter in human alcoholics and alcohol-exposed rats. Silvia de Santis

The study focused on two groups: humans and rats. The human group included 90 male patients over the age of 46 who were hospitalized for alcohol use disorder. There was also a comparative group of 36 healthy men who were an average age of 41. The researchers scanned the brains of the patients with diffusion-weighted MRI and discovered that even though the group of 90 had been abstinent from alcohol for six weeks, there were still negative signs of change in the white matter of their brains.

To understand the exact nature of these alterations, the scientists got a closer look by examining rats who were trained to also be dependent on alcohol. After they’d also gone through a period of abstinence, the rats’ brains exhibited a generalized change in white matter, which were most intense in the sections called the corpus callosum and fimbria. The former is the bridge between the left and right sides of the brain, while the latter contains nerve fibers that communicate to the hippocampus.

The hippocampus, a brain structure vital to learning and memory, is well-known to be affected by heavy drinking. Studies have found that chronic drinking reduces the total volume of the hippocampus, making it harder for an individual to not only retain memories but also learn new things. Until now, it’s been unclear whether or not the hippocampus heals itself after heavy drinkers quit consuming alcohol.

Now it appears that the damages caused by alcohol are at least still apparent after six weeks of not drinking. This team plans on investigating further, though. They want to discover the underlying process that’s causing this change and examine what happens to a brain as people with alcohol abuse problems get sober. Research shows that after detoxification, a brain can bounce back, but it’s clear that things aren’t entirely healed.

Partial Abstract:

Importance: Although the detrimental effects of alcohol on the brain are widely acknowledged, observed structural changes are highly heterogeneous, and diagnostic markers for characterizing alcohol-induced brain damage, especially in early abstinence, are lacking. This heterogeneity, likely contributed to by comorbidity factors in patients with alcohol use disorder (AUD), challenges a direct link of brain alterations to the pathophysiology of alcohol misuse. Translational studies in animal models may help bridge this causal gap.

Conclusions and Relevance: Using a translational DTI approach, comparable white matter alterations were found in patients with AUD and rats with long-term alcohol consumption. In humans and rats, a progression of DTI alterations into early abstinence (2-6 weeks) suggests an underlying process that evolves soon after cessation of alcohol use.