How Does Alcohol Affect the Brain? (It’s Not Pretty)

Ever wonder, “What does alcohol do to your body?” Particularly, how does alcohol affect the brain? The truth is the damage goes far beyond a headache and brain fog you experience the morning after drinking too much. The effects of alcohol on the brain are profound, and heavy drinking can set you up for some of the most dreaded brain diseases. The long-term effects of alcohol can completely rewire your brain, too, increasing the risk of depression and other conditions.

The Link Between Alcohol & Dementia

How alcohol affects the brain is likely more complex than most people think. True, it’s well known that the chronic use of excessive alcohol can have detrimental effects on the body. Still, a surprising 2018 French study from shows a strong link between early onset dementia, in which an individual begins shows symptoms of dementia before the age of 65, and alcohol addiction.

The study states that heavy alcohol use, as well as other alcohol use disorders, are important risk factors for dementia which can shorten lives by up to 20 years, with dementia as the leading cause of death.  

So how exactly are dementia, which up until now was mainly synonymous with Alzheimer’s disease, and alcohol-related?  To understand the link between the two, it is first helpful to understand the effects that alcohol has on the brain as a whole. (1, 2)

Alcoholism

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Heavy drinking is considered three drinks a day for women and four to five drinks per day for men. (3) There are several factors that determine how alcohol affects the brain: (4) 

• How much and how often drinking occurs
• Age when drinking first began
• Prenatal alcohol exposure
• Age, gender, genetic background/family history
• Level of education
• General health status

Symptoms of alcoholism are:

Physical

• Poor coordination
• Slurred speech
• Slowed reaction times

Psychological

• Impaired thinking
• Memory loss

Behavioral

• Engaging in risky behaviors
• Addictive behavior
• Depression

Withdrawal or abstinence of drinking results in sweating, nausea, shakiness, anxiety, and delirium tremens; which may include visual or auditory hallucinations. Immediate effects of alcohol are similar following a few drinks.

When you consume alcohol your liver breaks it down into nontoxic byproducts but with excessive consumption, your liver is unable to keep up with the demands required and the alcohol remains in the bloodstream. The effects of alcohol on the brain depends upon an individual’s blood alcohol concentration (BAC). (5)  

How Does Alcohol Affect the Brain?

An increase in BAC interacts with the brain through the blood-brain barrier.  Once in the central nervous system, alcohol causes alterations in behavior by acting upon specific regions in the brain susceptible to chemical modifications.

Regions of the Brain Affected by Alcohol

Mesolimbic pathway 

Alcohol stimulates the mesolimbic pathway, or the reward pathway, within the brain and releases dopamine causing a feeling of pleasure.  

This pathway is the major pathway involved with addiction in which constant stimulation of the pathway requires more of a substance to create the same level of pleasure. Studies have shown that a pathway that is repeatedly activated, in this case by drinking, becomes covered by a mesh-like glue that makes it difficult to form new synapses or break old ones. This explains why addiction is so tough to overcome, the pattern is ingrained and held together that way in the brain. (6, 7)

Frontal Lobe & Prefrontal Cortex 

This region is involved in decision making, motivation, planning, goal setting, judgment problem solving, social conduct and impulse inhibition.  Neuropathological studies have shown a large reduction in the number of neurons in the prefrontal cortex of alcoholics and overall reduced brain mass relative to controls (non-alcohol drinkers). (8, 9) Damage to the frontal lobe/prefrontal cortex results in emotional and personality changes.          

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Hippocampus 

The hippocampus lies within the mesolimbic system and is involved in motivation, spatial navigation, emotion and crucial for the formation of memories. (10) There is evidence that the hippocampus may also play a role with fear and anxiety. (11) The hippocampus is also one of the few sites for neurogenesis in the adult brain.  

Neurogenesis is the process of new brain cells being formed from stem cells (undifferentiated cells that can give rise to all different types of cells). Studies suggest that increasing doses of alcohol create a disruption in the growth of new cells, which leads to a deficit in specific areas such as the hippocampus which will lead to decreased learning and memory. (12) Hippocampal neurogenesis is resilient and has been shown to recover following 30 days of abstinence.  Though there appears to be increased vulnerability to relapse. (13)

Hypothalamus 

Also a part of the limbic system, the hypothalamus has connections to many systems and is involved in learning and memory, regulatory functions, eating/drinking, temperature control, hormone regulation and emotion.  Long-term damage to the hypothalamus due to alcohol leads to memory deficits and amnesia can follow. (14)

Cerebellum 

The cerebellum accounts for approximately 10 percent of the total weight of the brain but contains about half of the neurons. (15)  Small but mighty, the cerebellum coordinates voluntary movement, balance, eye movement and integrated into the circuitry for cognition and emotion.  Alcohol abuse leads to atrophy within the white matter of the cerebellum. (16)

Amygdala 

Within the temporal lobe, the amygdala has connections to the prefrontal cortex, the hippocampus and the thalamus and mediates emotions (love, fear, rage, anxiety) and helps identify danger.

How Does Alcohol Affect the Brain: Alcohol & Neurotransmitters

Alcohol affects the brain chemistry by altering the levels of neurotransmitters within the above-mentioned regions.  

Neurotransmitters are the chemical messengers within the brain that transmit signals within the central nervous system and extend out throughout the body.  The alterations of neurotransmitters within the specific regions cause changes in an individual’s behavior and motor functions.  

Neurotransmitters are either excitatory and increase electrical activity in the brain or they are inhibitory or decrease electrical activity in the brain.  

GABA and NMDA Receptors 

Alcohol slows the brain down by binding to the inhibitory GABA  and NMDA receptors.  This slow down results in slurring of words, decreased memory and tiredness.  (17)

Dopamine 

An excitatory neurotransmitter that is increased within the mesolimbic pathway, mediating the reward circuitry.

Norepinephrine 

The release of norepinephrine in conjunction with the temporary increases adrenaline, cortisol and dopamine creates a stress-free, party feeling. (18)  Chronic alcohol abuse results in a decrease in these neurons that release norepinephrine, which leads to impaired attention, information processing and a negative effect on learning and memory. (19)

Glutamate  

Glutamate is an excitatory neurotransmitter but is blocked from binding to its NMDA receptor by alcohol.  The inability to bind to its receptor leads to overall depressant effects throughout the brain. (20)

Serotonin 

Another excitatory neurotransmitter involved in the pleasure/reward effects of the mesolimbic pathway. Studies have shown a 50 percent reduction in serotonergic cells with chronic alcohol abuse, leading to alterations in mood, thinking, appetite, and sleep. (21)

Following the initial increase of the excitatory neurotransmitters, the stimulation wears off and there is a build-up of the inhibitory neurotransmitters; GABA and NMDA. This results in the depressed, subdued and tired “afterglow” of a night of binge drinking.  

Alcohol-Related Syndromes

Following chronic excessive alcohol consumption studies have shown an overall decrease in neuronal density, regional blood flow volumes and glucose metabolism.  (22, 23, 24)

The decrease in glucose metabolism as a result of alcohol consumption is due to a decrease in thiamine.  Thiamine (also known as vitamin B1) is critical for all tissues in the body, especially the brain.  The brain needs thiamine because of its critical role in glucose metabolism and neurotransmitters synthesis. (25) 

A decrease in thiamine can occur in two ways due to alcohol consumption.  One is a poor diet and the other is due to a decrease in thiamine absorption and activation. The body does have reserves of thiamine, but they become depleted during heavy drinking. If heavy drinking becomes chronic those reserves don’t have to ability to recoup and an individual starts to have a thiamine deficiency. Of the people with a thiamine deficiency due to alcohol consumption, 80 percent will go on to develop:

Wernicke Encephalopathy 

A person with Wernicke Encephalopathy will suffer from mental confusion, oculomotor disturbances (disturbances with muscles that move the eyes), and difficulty with muscle coordination. (26) 

Korsakoffs Psychosis 

Effects 80 to 90 percent of individuals with Wernicke encephalopathy.  Individuals showing symptoms of Korsakoffs Psychosis have difficulty walking and severe problems with amnesia, particularly anterograde amnesia or forming new memories. (27)

Alcohol-Related Dementia

Research shows the risk of developing dementia is three times greater in heavy drinkers than other people.  Dementia due to alcohol encompasses both Wernicke encephalopathy and Korsakoffs psychosis. (28)

Other syndromes due to alcohol consumption are:

• Hepatic Encephalopathy: Liver dysfunction occurs following chronic excessive alcohol abuse leading to changes in sleep patterns and mood, in addition to shaking hands and shortened attention span. (29)  The liver damage caused by alcohol results in an increase of ammonia in the blood which has a neurotoxic effect on the brain. (30)
• Cerebellar Syndrome with Anterior Superior Vermal Atrophy: Patient presents symptoms of a broad-based gait, difficulty with eye movements and dysarthria (slowed or slurred speech). (31)

Final Thoughts on How Does Alcohol Affect the Brain

• Excessive use of alcohol causes a variety of chemical and molecular alterations within the brain that forms the basis of several behavioral and physical manifestations.  
• The neurotoxic effects of alcohol lead to thiamine deficiency and global cell death within, particularly vulnerable areas within the brain.  
• This cell death results in a decrease in overall brain volume, specifically within the frontal lobe/prefrontal cortex, cerebellum and hippocampus.  
• Due to neurogenesis, abstinence of alcohol over an extended period of time may see a restoration of cells within these areas.  
• Lastly, although the research illustrating a link between early onset dementia and alcohol is in its early stages, it is a strong warning of the ever-growing list of detrimental effects of excessive alcohol consumption.  

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