Drinking alcohol grew into a socially acceptable activity in multiple societies, starting in the Neolithic period. From the earliest traces of brewing, which happened about 10,000 years ago, to former trade negotiations and family celebrations – the use of alcohol intertwined with people’s everyday life.
In the U.S., data from the 2019 National Survey on Drug Use and Health (NSDUH) shows that over 85 percent of adults aged 18 and older admitted to drinking alcohol at some point in their life, with more than 25 percent engaging in binge drinking. And although light-to-moderate drinking may bring some health benefits, including lowering the risk of heart disease and reducing stress, long-term excessive drinking can wreak havoc on the brain.
But when does the line between a couple of occasional drinks and heavy drinking begin to blur? How much is too much for alcohol to start affecting the brain?
How Alcohol Affects the Brain and Behavior
Having a pint of alcohol doesn’t necessarily mean you are “binge drinking.” According to the National Institute on Alcohol Abuse and Alcoholism (NIAAA), a person engages in binge drinking if they consume alcohol to a point where it brings their blood alcohol concentration (BAC) to 0.08 g/dL or higher. That would be the equivalent of five or more drinks for men and four or more for women within two hours of the same occasion.
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And when someone drinks, the alcohol reaches crucial areas of the brain — cerebral cortex, frontal lobe, hippocampus, hypothalamus, cerebellum — which impairs a person’s balance, judgment, speech and memory, and forces the brain to work harder. With time, increasing the BAC levels might be enough to create long-term effects on the brain.
Whether in the short run or long haul, how alcohol affects the brain depends on many factors. The amount of alcohol someone drinks, how often they drink, at what age they started drinking, family history, gender, genetics and health status are some of the most common triggers.
Short-Term Effects of Alcohol on the Brain
In the short term, there are many forms of how alcohol affects the brain. Alcohol skews the person’s senses. At first, you tend to become more confident as alcohol acts as a depressant in the cerebral cortex (which controls inhibition) and reaches no-go receptors in the brain, inducing the release of dopamine – the chemical responsible for pleasure.
Depending on the amount of alcohol you consume, you may then experience slurred speech, waddling, impaired vision, confusion and memory issues. In extreme cases, you could put yourself in danger.
An alcohol-induced blackout is another way alcohol affects the brain. If a person doesn't remember details of a conversation they had with you during a night of drinks, or, they barely recall things they did or said, there is a big chance they had a blackout.
Aaron M. White, a former assistant professor from the Department of Psychiatry at Duke University Medical Center, defines blackouts as “periods of memory loss for events that transpired while a person was drinking.”
Alcohol-induced blackouts happen when alcohol prevents the consolidation of memories in the hippocampus, and the individual’s drinking pattern impairs the transfer of short-term memory to long-term memory. This process usually occurs with a BAC of 0.16 percent, or higher, and depends on other factors, such as how quickly the person can drink or if they drink on an empty stomach.
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Long-Term Effects of Alcohol on the Brain
There is no lack of literature exposing the long-term effects of alcohol on the brain. Studies have shown that the heavy, prolonged consumption of alcohol can trigger mental health issues, including anxiety and depression, and can lead to alcohol use disorder. But this is not all. Scientists are taking a proactive approach to understanding the alcohol role in brain shrinkage, as well as other severe brain disorders.
As alcohol hinders communication pathways, compromising brain functioning, researchers have found that long-term heavy drinking leads to changes in the neurons (including their size), causing “brain shrinkage.”
After observing the alcohol consumption and brain health from a group of around 427 participants in a longitudinal cohort study over 30 years, researchers from the University of Oxford concluded that shrinkage in the brain was directly related to the amount of alcohol someone ingested. Essentially, while the participants who consumed four or more drinks daily had a higher risk of “hippocampal atrophy,” or an early sign of Alzheimer’s disease — six times more than “abstainers” — the study showed a three-time risk for moderate drinkers.
While we know that excessive use of alcohol harms the brain, other non-direct factors are proven culprits, such as when a person suffers from a lack of thiamine. Studies have shown that chronic alcohol consumption leads to thiamine (vitamin B1) deficiency (80 percent of people who struggle with alcoholism have it), stemming from poor nutrition and hampered absorption of thiamine from the gastrointestinal tract. The problem?
Thiamine — found in bread, whole grains, fortified cereals, meat, poultry, nuts and beans, among other foods — is an essential nutrient crucial for the proper activities of enzymes in the tissues, among other roles.
The most extreme case of its deficiency can cause a severe brain condition called Wernicke–Korsakoff syndrome — characterized by mental confusion, abnormal eye movements, trouble with coordination (short-term symptoms are called Wernicke’s encephalopathy); and memory issues and amnesia (long-term symptoms are known as Korsakoff’s psychosis).
Chronic Liver Disease - Hepatic Encephalopathy
Chronic liver disease, or cirrhosis, is another example of how alcohol affects the brain, but in a drastic way. The heavy and prolonged use of alcohol — which can harm the liver, causing liver disease — may also give rise to a critical brain disorder called hepatic encephalopathy.
During hepatic encephalopathy, the liver fails to break down alcohol, letting excess amounts of manganese and ammonia enter the brain. Besides creating cognitive, coordination and personality issues, hepatic encephalopathy can also be fatal.
Though the short-term effects of alcohol can subside once you stop drinking, in the long run, reversing how alcohol affects the brain is still up for debate among researchers. So, if you want to maintain a healthy brain, preventing alcohol misuse is the best alternative for now.