Alcohol is toxic to the brain, and alcohol poisoning can damage its structure and function. Acute alcohol poisoning can quickly degenerate into a life-threatening medical emergency or death, because of the acute damaging effects on the brain. In addition, the toxin can lead to long-term damage in vulnerable areas of the brain. Be aware of the early signs of alcohol poisoning so you know when to call for help.
Alcohol Poisoning and the Brain
Alcohol poisoning from drinking a larger amount of alcohol than the liver can metabolize leads to a high blood alcohol level that adversely affects the brain and other organs. This problem is of particular risk among high school and college teens who might indulge in episodes of excessive alcohol intake in a short time span, or binge drinking.
The toxic level of alcohol impacts the brain directly or indirectly through its effects on the liver, and through the consequences of low oxygen supply to the brain (hypoxia). Most published reports on alcohol poisoning describe the acute brain effects in detail. However, there is little written on long-term brain damage and consequences in humans, but animal studies provide some insights.
Acute Damaging Effects on the Brain
According to a National Institute on Alcohol Abuse and Alcoholism (NIAAA) factsheet, the acute damaging effects of alcohol poisoning on the brain depress the brain centers that control vital systems, such as the function of the heart and lungs, temperature balance, and gag reflex. This leads to a constellation of difficulties, including:
- Irregular or slow breathing and eventually, breathing might stop
- Irregular or slow heartbeat, which can lead to inadequate brain oxygen supply
- Low body temperature (hypothermia), and cold, pale bluish skin tone
- Inadequate blood sugar (hypoglycemia) to provide vital fuel for the brain
- Severe vomiting because of alcohol's effects on the central nervous system and irritation of the stomach
- Risk of death from choking on vomit because of the diminished gag reflex, which can lead to aspiration of food into the lungs, causing asphyxia
- Severe confusion and disorientation, which can progress quickly to a "blackout" or unresponsiveness
Together with severe dehydration, electrolyte imbalance, and low blood sugar, the resulting brain hypoxia can lead to brain damage, seizures, coma, and death. Information on the effect of alcohol poisoning on the human brain can be gleaned from behavioral observations, and from modern imaging studies and autopsy findings.
Chemical and Functional Changes
A report published in 2009 in an Oxford Journal on Alcohol and Alcoholism reviews animal and other studies on the effect of excess alcohol on the brain. The authors suggest toxic levels of alcohol, as in binge drinking, cause immediate damage to the brain. This affects nerve pathways and neurotransmitters by which nerve cells and areas of the brain communicate with each other.
Alcohol's toxicity changes how the brain functions by primarily affecting the following neurotransmitter signalling systems:
- Glutamate: Alcohol increases glutamate levels in areas of the brain. Glutamate's role is to excite nerve cells, and excess causes cell death by increasing calcium and sodium influx into the cell and by causing oxidative stress.
- Gamma-aminobutyric acid (GABA): Decrease in this inhibitory can cause excitation of nerve cells in the brain and lead to anxiety.
- Dopamine: There is an increase in dopamine release in the limbic, or reward, pleasure, and motivation system. When the alcohol wears off, decrease in dopamine can cause prolonged depressed mood and malaise.
- Serotonin: This regulates mood, sleep, eating, and other behaviors. Alcohol increases serotonin release, affecting mood and behavior.
Other complex biochemical changes also occur that may contribute to nerve cell injury or death. In humans, functional changes can be investigated by MRI or PET scan.
Structural Changes
Much of the information on the structural changes that are possible in humans from alcohol poisoning comes from animal studies, such as one reported in the journal Alcoholism, Clinical and Experimental Research. Alcohol poisoning, or chronic heavy drinking, can cause:
- Death or shrinkage of brain nerve cells, causing the gray matter of the brain to shrink
- Shrinkage of the finger-like projections (dendrites) and nerve fibers (axons) that connect nerve cells to each other, which interrupts neurotransmitter signals between them, adding to the functional changes. This causes reduction in white matter.
In humans, evidence of the structural changes that excessive alcohol causes can be investigated by imaging studies such as CT and MRI brain scans, or during autopsy.
Affected Areas of the Brain and Consequences
Another NIAAA report notes alcohol is a toxin to the entire brain, but the most vulnerable areas to structural and functional damage and the consequences include:
- The frontal lobes are the most vulnerable of all to alcohol poisoning. This is especially true of the prefrontal cortex, which can lead to impairment in higher (executive) human functions such as:
- Decision-making and reasoning
- Judgement and insight
- Behavior and impulse control
- The limbic system may be damaged, which can lead to mood disturbances, such as depression and anxiety, and decreased cognitive function
- Cerebellum damage can lead to impaired motor coordination and balance.
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Hippocampus damage affects long-term memory, learning, concentration, focus, and motivation.
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Thalamus damage may affect processing and relay of information to the cerebral cortex.
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Hypothalamus damage interferes with temperature and appetite control, and with hormone production and secretion.
Long-Term Brain Damage
Damage to these brain areas by alcohol poisoning can lead to short- or long-term difficulties with behavior, learning, concentration, short-term and long-term memory, and a risk for impulsivity, mood disturbances, psychotic breaks, and early dementia. Whether alcohol poisoning causes irreversible damage to the brain's structure and function depends on how severe the poisoning was and other individual factors.
Varying Degrees of Damage
In the absence of factors like liver or kidney disease or poor nutrition, prompt treatment - before significant, prolonged brain hypoxia and lack of fuel - might prevent severe and permanent structural and chemical brain damage or death.
Those who survive might suffer long-term from varying degrees of the direct toxic effects of alcohol and hypoxia on the brain, depending the amount of alcohol taken and other factors in the affected person. According to the National Institutes of Health, teens are especially at risk for long-term brain effects of toxic levels of alcohol.
Potential for Repair of Brain Damage
Scientists now know that new nerve cells (neurogenesis) can develop from stem cells in the brain to replace ones that died, hence the ability of the brain to recover from an insult like alcohol poisoning. Depending on the damage and health factors, some people's brains may repair themselves from the alcohol poisoning and show few or no signs of damage. Others might continue to show signs of persistent damage because of irreversible structural, biochemical, and functional changes in areas of the brain.
Factors That Affect Alcohol-Related Brain Damage
The amount of alcohol that is toxic and the degree of subsequent brain damage varies from person to person and depends on a number of factors, such as:
- Age: Teenagers especially are more vulnerable to the toxic effects of binge drinking.
- Gender: Women appear to be more vulnerable to the damaging effects to alcohol than men.
- Previous drinking history: New drinkers are more likely to be affected by excessive alcohol consumption than chronic drinkers or alcoholics.
- Food intake: Food in the stomach slows down the absorption of alcohol into the blood.
- Existing thiamine deficiency makes the brain more vulnerable to alcohol toxicity.
- Existing liver disease impairs alcohol metabolism, causing greater blood alcohol levels.
- Genetics play a great role in individual response to alcohol.
- Individual vulnerability of specific areas of the brain also plays a role.
Blood Alcohol Level and Brain Effects
The blood alcohol content (BAC) threshold before poisoning and brain damage occurs is different for each person. In general according to the National Institute on Alcohol Abuse and Alcoholism factsheet, the following guideline is useful:
- BAC legal limit for driving in the USA = 0.08% (80 mg/dL)
- Signs and symptoms of early alcohol brain impairment = 0.06% to 0.15% (60 to 150 mg/dL)
- Symptoms of alcohol poisoning and severe brain impairment= 0.16 % to 0.30% (160 to 300 mg/dL)
- Significant risk of death from alcohol poisoning = 0.31% to 0.45% (350 mg/dL) or higher
Age and prior alcohol use affect the BAC at which alcohol poisoning and severe brain damage can occur. In the book, Alcohol and Its Biomarkers, the authors note alcohol poisoning can occur in children and non-alcoholic adults at a BAC as low as 0.10% (100 mg/dL), whereas alcoholics may not reach poison level until 0.30% (300 mg/dL). They also state that an increased risk for coma can occur starting at a BAC of 0.25% (250 mg/dL).
Avoid Alcohol Poisoning
Avoid consuming a large amount of alcohol in a short period. Alcohol is highly toxic, and heavy drinking that leads to alcohol poisoning causes immediate damage to the brain and body. This can cause irreversible brain abnormalities in those who survive.
