How Alcohol Causes Brain Shrinkage

Cold beer
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Multiple research studies have found that the brains of people with severe alcohol use disorder are smaller and lighter than the brains of those who do not have this condition. This brain shrinkage affects the networks that regions of the brain use to communicate with other regions; the parts of the brain that allow neurons to communicate with neighboring neurons are also affected.

Some Damage Is Reversible

Although chronic alcohol misuse causes significant brain damage, abstinence can reverse some (but not all) of that. With appropriate interventions, people with alcohol use disorder can attain long-term sobriety despite deficits in decision-making.

How Alcohol Causes Brain Shrinkage

The gray matter of the brain in the cerebral cortex controls most of the brain's complex mental functions. The cortex is filled with neurons that connect by fibers to different regions of the brain and to other neurons inside the brain and spinal cord. The nerve fibers are the white matter of the brain—the "hard-wiring."

These nerve fibers have shorter, more numerous fibers called dendrites that branch out like the roots of a tree to allow the neurons to "talk" with other neurons. A neuron can communicate with as few as five or as many as 10,000 other neurons at a time.

These two parts of the brain—the white matter and the dendrites—are most vulnerable to the shrinkage that alcohol misuse can cause.

Of course, brain shrinkage is not the only damage alcohol misuse can do to the brain. Alcohol can cause chemical changes that affect the function of neurotransmitters.

How Alcohol Affects the Brain

Chronic alcohol misuse creates complex, toxic metabolic and nutritional interactions that can cause mental deficits. Some of these are still not understood completely:

  • Acetaldehyde, a metabolite of alcohol, could cause toxic effects.
  • Malnutrition, especially thiamine deficiency, could play a role.
  • Cirrhosis of the liver can also cause brain damage.
  • Head injury and sleep apnea can contribute to brain damage.

Alcohol, thiamine deficiency, and cirrhosis are linked. Some researchers believe they contribute in a complex manner to brain damage.

Is Brain Shrinkage Permanent?

Some of the damage done to the brain by alcohol can be reversed once the person stops drinking and maintains a period of abstinence, but some of it is permanent and cannot be undone.

The most significant permanent damage caused by alcohol is nerve cell loss. Some nerve cells cannot be replaced once they are lost, and that includes those in the frontal cortex, cerebellum, and other regions deep inside the brain, according to research.

However, abstinence can help reverse the shrinkage of dendrites, which studies have shown will begin to grow again and spread after weeks or months of abstinence. This has been linked to improved brain function.

When cirrhosis of the liver is treated, some of the brain damage it can cause can begin to reverse. Brain damage due to thiamine deficiency in people who misuse alcohol can easily be treated with thiamine, but repeated deficiencies can cause permanent damage.

Impact of Brain Shrinkage Cause by Alcohol Use

One reason that people with alcohol use disorder are so prone to relapse is the damage it causes to the brain's reward system and decision-making abilities. The result is that the drinker is more motivated by immediate rewards than delayed rewards. Addictive substances such as alcohol provide immediate intoxicating rewards.

Chronic alcoholism chemically changes the brain's reward system to the point that the drinker's pursuit of rewards becomes pathological.

Long-term heavy alcohol consumption affects the brain's frontal lobe functions, which include inhibition, decision-making, problem-solving, and judgment. This kind of brain damage makes it difficult to maintain long-term sobriety.

However, people with alcohol misuse disorder can overcome these impairments with abstinence, which helps reverse the damages. They then can achieve long-term, multi-year sobriety when motivated to do so.

If you or a loved one are struggling with substance use or addiction, contact the Substance Abuse and Mental Health Services Administration (SAMHSA) National Helpline at 1-800-662-4357 for information on support and treatment facilities in your area.

For more mental health resources, see our National Helpline Database.

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9 Sources
Verywell Mind uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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Additional Reading
  • Bartsch, AJ, et al. "Manifestations of early brain recovery associated with abstinence from alcoholism." Brain.

  • Harper, C, et al. "The Pathophysiology of 'Brain Shrinkage' in Alcoholics—Structural and Molecular Changes and Clinical Implications." Alcoholism: Clinical & Experimental Research.

  • Siggins, GR, et al. "Ethanol Augments GABAergic Transmission in the Central Amygdala via CRF1 Receptors." Science.