A new study suggests that a single episode of extreme drinking in young adults may be linked to almost immediate structural brain atrophy. Adolescence and emerging adulthood are known to represent critical stages for brain development, involving heightened vulnerability to the toxic effects of drinking. Chronic alcohol use among young adults is associated with structural brain abnormalities, especially in the corpus callosum, which transfers information between brain hemispheres—a key function in learning and memory.

The study, published in Alcoholism: Clinical and Experimental Research, assessed participants before and after a single episode of extreme drinking—consuming more than four to five alcohol-containing beverages in a single episode—scanning the brain for changes. Fifty undergraduate students underwent an MRI scan less than two weeks before their 21st birthday celebrations—an occasion when many Americans drink heavily. A few days after their celebrations, they had a second MRI scan and were interviewed about their alcohol use.

Researchers used drink-by-drink reconstruction to estimate the participants’ peak blood-alcohol concentration (BAC) during the celebrations and identify who had experienced an alcohol-induced blackout. Five weeks later, investigators re-scanned 29 students. They used statistical analysis to explore associations between alcohol use during the celebrations, the MRI findings, and the students’ histories of drinking and cannabis use.

Most of the participants drank heavily during their birthday celebrations. The MRI scans found changes to participants’ brains that appeared to be specifically associated with their alcohol use during these celebrations. The more that participants drank, the more atrophy was detectable in their posterior corpus callosum, notwithstanding their alcohol and cannabis use histories.

The 17 participants who had experienced a blackout showed greater loss of volume in this brain region than those who did not. Damage to the corpus callosum has been linked to reduced cognitive performance and higher rates of drinking relapse, among other effects; previous studies have also found decreased volume of the corpus callosum in people with alcohol use disorder.

The MRI scans of 29 participants five weeks later did not reveal further structural atrophy or recovery in the corpus callosum (this may be explained by the lower number of participants). This study did not detect alcohol-related damage to other brain regions that are considered vulnerable, including the hippocampus.

The findings underscore the importance of intervention and prevention programs aimed at young adults who may experience extreme drinking. Future research is needed to understand whether these structural brain changes are long-lasting and associated with behavioral or cognitive consequences.