Alcohol begins affecting a person's brain as soon as it enters the bloodstream. In a healthy person, the liver quickly filters alcohol, helping the body get rid of the drug. However, when a person drinks to excess, the liver cannot filter the alcohol fast enough, and this triggers immediate changes in the brain.

Over time, excessive alcohol consumption can damage both the brain and liver, causing lasting damage.

Excessive alcohol consumption can have long-lasting effects on neurotransmitters in the brain, decreasing their effectiveness or even mimicking them. Alcohol also destroys brain cells and contracts brain tissue. Some people with a history of excessive alcohol use develop nutritional deficiencies that further damage brain function.

The precise symptoms of alcohol-related brain damage depend on a person's overall health, how much they drink, and how well their liver functions, among other factors.

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Moderate consumption of alcohol may cause a depressed mood, loss of inhibition, and sleepiness.

As soon as alcohol enters the bloodstream, it changes how the brain functions. Moderate consumption of alcohol may cause the following temporary effects:

  • loss of inhibition
  • decreased planning and organizational skills
  • changes in mood and concentration
  • difficulty forming new memories
  • sleepiness
  • depressed mood
  • changes in energy levels
  • memory loss
  • poor judgment
  • reduced motor control, including delayed reflexes that can make driving dangerous

People with severe symptoms of intoxication or symptoms that last many hours are at risk of alcohol poisoning.

The ethanol in alcohol acts like a poison. When the liver is not able to filter this poison quickly enough, a person can develop signs of alcohol poisoning or alcohol overdose. An overdose of alcohol affects the brain's ability to sustain basic life functions.

Symptoms include:

  • vomiting
  • seizures
  • slow heart rate
  • difficulty staying awake
  • fainting
  • low body temperature
  • low gag reflex, which can increase the risk of choking if a person vomits
  • clammy skin

An untreated alcohol overdose can be fatal. Severe alcohol overdoses may cause permanent brain damage even if the person survives.

The higher a person's blood alcohol concentration, the higher their risk of alcohol overdose. The heavy consumption of high-alcohol drinks is more likely to cause alcohol poisoning. People who have smaller bodies, drink alcohol less frequently, or have a history of liver disease are also more vulnerable to alcohol poisoning.

Over time, alcohol abuse can cause permanent brain damage.

Wernicke-Korsakoff syndrome

One form of alcohol-related brain damage is Korsakoff syndrome. Korsakoff syndrome often appears after an episode of Wernicke's encephalopathy, which is acute alcohol-related brain dysfunction.

The two conditions, together called Wernicke-Korsakoff syndrome, happen in people who are severely deficient in thiamine (vitamin B-1). Alcohol abuse makes it more difficult for the body to absorb this nutrient, but other issues, such as severe eating disorders, cancer, AIDS, and conditions that affect the body's ability to absorb nutrients, may also cause Wernicke-Korsakoff syndrome.

Some symptoms of Wernicke's encephalopathy include:

  • confusion and disorientation that continue well beyond the period of drunkenness
  • malnourishment that may cause significant weight loss
  • trouble moving the eyes or strange and jerky eye movements
  • poor balance

Following Wernicke's encephalopathy, the person may develop signs of Korsakoff syndrome. This disorder is a type of dementia.

Symptoms include:

  • memory problems, in particular, difficulties forming new memories
  • poor judgment
  • decreased planning and organizational skills
  • mood and personality changes
  • hallucinations
  • progressively worsening cognitive decline that may affect every area of functioning, including speech, vision, and bowel and bladder function

Vitamin supplements and complete abstinence from alcohol may reverse symptoms of Wernicke-Korsakoff syndrome within the first 2 years after stopping drinking.

Fetal alcohol syndrome

Fetal alcohol spectrum disorders, which people usually refer to as fetal alcohol syndrome, happen when a developing baby gets exposure to alcohol during gestation. Fetal alcohol syndrome affects many aspects of functioning, and it can cause brain damage.

The symptoms vary in severity, but may include:

  • intellectual disabilities
  • hyperactivity
  • poor memory
  • trouble concentrating
  • weak coordination
  • vision and hearing issues

Doctors have not yet established a safe level of alcohol consumption during pregnancy, so the best strategy for preventing fetal alcohol syndrome is to abstain altogether from alcohol at this time. If a pregnant woman cannot abstain, she should aim to reduce her alcohol consumption as much as possible.

Head injuries

Alcohol is a risk factor for traumatic brain injuries (TBI) due to falls, car accidents, fights, and other blows to the head. According to a 2010 analysis, 35–81% of people who seek treatment for a TBI are intoxicated.

In the short term, a head injury can cause confusion and disorientation. It may also result in dangerous brain swelling. Severe head injuries may even be fatal because they affect the brain's ability to control essential functions, such as breathing and blood pressure.

The long-term effects of head injuries vary but may include:

  • dementia-like symptoms, such as difficulties forming new memories
  • changes in mood or behavior
  • increased risk of developing Alzheimer's disease and Parkinson's disease
  • changes in blood flow patterns in the brain

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Common psychological effects of drinking alcohol include trouble concentrating, mood changes, and depression.

Alcohol has numerous psychological effects, including:

  • personality and mood changes
  • changes in impulse control
  • trouble concentrating
  • depression

Perhaps the most significant psychological effect, however, is addiction. Over time, people who consume large quantities of alcohol develop a tolerance to the drug. They also become dependent. This dependency means that their brains crave the drug, causing them to experience withdrawal when they do not drink.

Addiction leads a person to continue using alcohol, even when it harms them. People with severe alcohol use disorder may develop a dangerous withdrawal condition called delirium tremens (DT). DT begins with psychological symptoms that include:

Without treatment, DT can be fatal in more than one-third of people whom it affects. People with DT may experience seizures, dangerous changes in blood pressure, and excessive vomiting and diarrhea, which can result in nutritional deficiencies.

Alcohol does more than harm the brain. Both severe intoxication and long-term abuse can damage virtually every system in the body. The physiological effects of alcohol include:

Although alcohol can cause significant brain damage, an emerging body of research suggests that modest alcohol consumption may be beneficial for the brain.

A 2018 study that followed 9,087 participants for 23 years found that people who did not drink alcohol in midlife were more likely to develop dementia. Dementia risk was lowest among those who consumed 14 or fewer units of alcohol per week.

The 2015–2020 U.S. Dietary Guidelines for Americans recommend no more than one drink per day for women and no more than two drinks per day for men. People who should avoid alcohol include those who:

  • are recovering from alcohol use disorder
  • are taking drugs that interact with alcohol
  • are pregnant
  • have certain liver diseases
  • find it difficult to control their drinking

As safe alcohol consumption varies from person to person, and different sources recommend various intakes, it is important to take an individualized approach. People should talk to a healthcare professional about their drinking history and personal risk factors to get tailored advice on safe alcohol consumption.

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People with a history of alcohol misuse may wish to speak to their doctor about a medical detox.

People with a history of alcohol misuse may not be able to consume alcohol safely. In these cases, the best strategy is to avoid alcohol altogether.

People with severe addictions or a long history of alcohol misuse may suffer serious withdrawal symptoms when quitting. People should talk to a doctor about medical detox, which may prevent serious issues, such as delirium tremens. Some people find that inpatient rehab or support groups, such as Alcoholics Anonymous, are helpful.

People who want to cut back on alcohol should consider the following strategies:

  • setting a personal limit of one drink a day for women and two for men
  • only drinking at certain times or occasions, such as at parties or on the weekends
  • not using alcohol to cope with emotional stress or to fall asleep
  • drinking beverages with lower alcohol content, for example, by replacing spirits with wine

The effects of alcohol on the brain vary depending on the dose and on individual factors, such as overall health. In general, the more alcohol a person drinks, the more likely it becomes that alcohol will damage the brain — both in the short and long term.

Moderate alcohol consumption is the best strategy for reducing the risk of alcohol-related brain damage. People who binge drink, drink to the point of poor judgment, or deliberately become drunk many times each month have a much higher risk of alcohol-related brain damage.