The brain, alcohol and shrinkage


Size does matter. Or does it? When it comes to the most intelligent organ in the body, the brain, bigger is not always better. The brain reaches maturity and its largest size by the late second decade in a human’s life. As humans age, the brain slowly shrinks about 2 percent per decade. The average male adult brain weighs just under 3 pounds.

Although there are many brilliant species such as whales, elephants and dolphins with much bigger brains than the human brain, it is the brain-to-body mass that should be taken into account. Humans have a relative brain-to-body mass of about 2 percent compared to large mammals that have a brain-to-body mass of less than 0.1 percent.

Although there is some slight correlation with intelligence and brain size, brain size is not the primary determining factor of intelligence. Unlike animals, humans actively are aware and choose what we put in our bodies; it is not surprising that many studies have been done to look at the direct cause and effect of alcohol on brain size.

Alcohol shrinks brain volume

Alcohol is the most consumed drug in the United States and has a multitude of effects on almost every organ in the body. In very small doses, red wine has been shown to be protective to the heart, but in larger doses alcohol is a very common cause for a condition known as dilated cardiomyopathy, a condition in which the heart becomes large and floppy, and the muscle becomes weak and unable to pump blood throughout the body. Alcohol has also been shown to cause decreased brain volume in adults.

Individuals who drink alcohol have been shown to have a smaller brain volume over time compared to those who do not consume alcohol. CNN reported on a study published in the Archives of Neurology that examined about 2,000 healthy adults who were on average 60 years of age. They underwent MRI studies of their brains and completed surveys of how much alcohol they consumed. Results showed that the more alcohol consumed the smaller the brain volumes. The reason for this is not clear.

Alcohol dehydrates tissues, which causes them to shrink, but the researchers are not sure if this is actually the reason why brain volume decreases in drinkers. Alcohol plays a key role in a dementia known as Wernicke- Korsakoff disease, but this brain shrinkage and this disease have not been clearly linked.

Does that shrinkage matter?

The difference in brain size between drinkers and nondrinkers was very small — about 1.5 percent. This is not a huge decrease, and scientists are not sure whether this amount of shrinkage can actually contribute to memory and cognitive deficits. In fact, the direct correlation between brain size and intelligence is poorly linked and not well understood. So, although alcohol does shrink the brain, the consequences of that shrinkage still must be determined through research studies.

A therapeutic boarding school for adolescent males from age 12 through 17, White River Academy recognizes that the mind and body both play a role in behavioral health,  so we take a holistic approach to treating alcohol and substance abuse, numerous mental health disorders and co-occurring conditions. For more information, please call our 24/7 helpline.

About the author

Kristen Fuller, M.D., enjoys writing about evidence-based topics in the cutting-edge world of medicine. She is a physician and author, who also teaches, practices medicine in the urgent care setting and contributes to medicine board education. She is also an outdoor and dog enthusiast.

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