Alcohol is one of the most widely used psychoactive
substances in the world, and has been a part of different cultures for hundreds of years. Drinking alcohol can have serious harmful
consequences, it’s been linked to various cancers, gastrointestinal diseases, and metabolic
problems. Over time, regular use of alcohol can lead
to alcohol dependence and bouts of withdrawal, and this can take a serious physical and emotional
toll on a person’s life. Alcoholic drinks contain the chemical ethanol,
which is a tiny molecule that reduces the activity of various inhibitory and excitatory
neurotransmitter pathways in the brain. Inhibitory neurotransmitters make neurons
in the central nervous system less likely to fire an action potential, and the brain’s
major inhibitory neurotransmitter—gamma-aminobutyric acid or GABA—acts as an “off” switch
and restricts brain activity. Ethanol is a GABA agonist, so when it binds
to GABA receptors it makes that inhibitory signal even stronger. Ethanol also activates opioid receptors and
induces the release of endogenous morphine—known as endorphins. The opioids then bind to receptors on dopaminergic
neurons in the nucleus accumbens, which trigger the release of dopamine and serotonin in that
part of the brain. Ethanol also acts as a glutamate antagonist. In other words, ethanol blocks glutamate,
which is an excitatory neurotransmitter, from binding to glutamate receptors, making it
less likely that those neurons will fire. The combined effect that ethanol has on these
neurotransmitters varies by the location in the brain. For example, in the nucleus accumbens and
the amygdala, which are the reward centers of the brain, ethanol produces pleasant or
rewarding feelings like euphoria. This is important because if a person believes
that drinking leads to euphoria, they are more likely to drink again. In the cerebral cortex, the thought-processing
center of the brain, ethanol slows everything down, making it difficult to think and speak
clearly. Ethanol also slows behavioral inhibition centers
like the prefrontal cortex, making people feel more relaxed and less self-conscious. In the cerebellum, the area responsible for
movement and balance, ethanol causes individuals to lose their coordination, making it harder
to walk or do complex tasks like driving. Ethanol also affects the hypothalamus and
pituitary glands, which regulate various hormones and mood. In these areas, ethanol typically increases
sexual arousal, but decreases a person’s ability to engage in sex. In the medulla, which controls automatic functions
like breathing, consciousness, and body temperature, ethanol increases sleepiness, slows breathing,
and lowers the body temperature to a point where it’s life-threatening. Alcoholic drinks have varying amounts of ethanol. For example, 355 ml or 12 fluid ounces of
beer typically contains 5% ethanol by volume, 148 ml or 5 fluid ounces of wine has 12% ethanol
by volume, and 44 ml or 1.5 fluid ounces of 80-proof distilled spirits like gin, rum,
tequila, or whiskey contains 40% ethanol by volume, all three of these alcoholic drinks
therefore have about 18 ml of pure ethanol. Ethanol’s effects on a person are directly
related to the blood alcohol content, or BAC, which is the percentage of ethanol in a given
volume of blood. BAC is affected by the amount of ethanol consumed
as well as a person’s blood volume, which depends on their size and sex, as well as
situational factors like how much they’ve had to eat or drink, what other substances
or medications they may be using, and how well the body is prepared for the alcohol. At a blood alcohol content of 0.0 to 0.05%,
people typically feel relaxed and happy, but might have slurred speech, and some difficulty
with coordination and balance. At a blood alcohol content of 0.06 to 0.15%,
there is more impairment in speech, memory, attention, and coordination, and some individuals
can get aggressive and even violent. Complex tasks like driving can become dangerous,
which is why it is illegal to drive in some countries with a blood alcohol content of
0.08% or higher. At a blood alcohol content of 0.16 to 0.30%
individuals can experience alcohol poisoning with blackouts or periods of amnesia, vomiting,
or even a loss of consciousness. Finally, at a blood alcohol content above
0.31%, the effect of alcohol can severely suppress breathing and even lead to death. Over time, individuals who consistently use
alcohol can develop tolerance to its effects. This means that with repeated use, they have
a reduced response to alcohol, and therefore an increased dose is needed to achieve the
original response. At a cellular level, there are a couple theories
that explain why this might happen. One is that repeated exposure to ethanol may
cause GABA, glutamate, dopamine, and serotonin receptors to become less sensitive to alcohol. Another is that neurons may remove these receptors
from the cell wall in a process called down-regulation, leaving fewer receptors available for binding. In either scenario, tolerance leads to the
need for higher and higher doses of alcohol, and often times that tolerance stays for a
long time even after decreasing alcohol use. Now, let’s say that you’re at rest, without
alcohol or anything stimulating your reward pathway. In this situation, your brain keeps your heart
rate, blood pressure, and wakefulness in a normal state, called homeostasis. Now, let’s say that your secret crush sends
you a text. All of a sudden you may feel sweaty and flushed,
your heart rate may jump a bit. You’re now above your normal level of homeostasis,
because something has changed, right? But it doesn’t stay that way for long, and
after the text, your brain brings things back down to this baseline. With repeated alcohol use, a few things start
to happen. Let’s say you drink at a specific time and
setting, like 5pm in the kitchen, and, being a depressant, it makes everything go slower,
including heart rate, blood pressure, and wakefulness. Your brain, being the smart brain that it
is, will pick up on that pattern for next time. Now, next time, at 5pm in the kitchen, the
brain preemptively increases functioning, since it knows that when you drink the alcohol,
everything’s going to decrease. Now, let’s say 5pm in the kitchen rolls
around, but there’s no alcohol. In that situation, the brain still increases
heart rate and blood pressure, but the changes aren’t countered with the effects of alcohol,
and so the person can feel awful, and these are called withdrawal symptoms. These symptoms can persist, to the point where
a person may need alcohol just to feel normal, and if that’s the case, they are considered
to be dependent on alcohol. Now, on the flip side, let’s say that you
use alcohol in an unfamiliar setting, like at a party at 11pm. Well in that situation, your body’s not
ready for the alcohol and there’s no physiologic “counterbalance” to help offset the effect
of the alcohol. When that’s the case, it can lead to overdose,
even on a dose or amount that the person’s been normally taking, and that’s often times
what happens. Symptoms of alcohol withdrawal include can
include anxiety, depression, irritability, fatigue, tremors, palpitations, clammy skin,
dilated pupils, sweating, headaches, difficulty sleeping, vomiting, and even seizures. A severe complication of withdrawal, called
delirium tremens, can take place a few days into the alcohol withdrawal, and includes
symptoms like a high fever, intense agitation, visual hallucinations, and even tactile hallucinations
where it feels like something is crawling on the skin. These symptoms are so severe that they can
lead to death. So, given how awful alcohol withdrawal can
be, people will sometimes continue to drink simply to avoid them, a process called negative
reinforcement. Negative reinforcement or drinking more to
avoid discomfort, often combines with the positive reinforcement or drinking more to
increase feeling euphoric and leads to alcohol addiction or alcohol use disorder. Now, the DSM-5 (or the Diagnostic and Statistical
Manual of Mental Disorders, the 5th edition) defines alcohol use disorder as a maladaptive
pattern of alcohol consumption that includes at least two of the following behaviors within
the past year: 1. Consuming more alcohol than intended. 2. Being unable to cut down on alcohol use. 3. Having alcohol use take up a lot of time 4. Having cravings to use alcohol. 5. Having alcohol use affect responsibilities
6. Using alcohol even if it causes interpersonal
problems 7. Giving up important activities in order to
use alcohol. 8. Using alcohol in physically dangerous situations
(like while driving). 9. Using alcohol even if its worsening a physical
or psychological problem 10. Becoming tolerant to the alcohol. And 11. Feeling withdrawal symptoms from alcohol. Having 2 or 3 of these symptoms is considered
mild, having 4 or 5 is considered moderate, and having 6 or more is considered severe. Even mild alcohol use disorder can be debilitating
because of the negative effects it can have on a person’s ability to function at work
or in relationships. In addition, alcohol use disorder has serious
long-term health consequences. Chronic alcohol use can damage the heart,
causing dilated cardiomyopathy—where the heart muscle stretches out and like a large
floppy sack. This also leads to other problems like arrhythmias
or irregular heartbeat as well as strokes. Chronic alcohol use can also cause inflammatory
changes in the liver affecting its ability to function. The complications include steatosis, steatohepatitis,
fibrosis, and cirrhosis. Similarly it can cause pancreatitis—inflammation
of the pancreas. Alcoholism is associated with the risk of
developing certain cancers, including mouth, esophagus, throat, liver, and breast cancer. Finally, it’s common to see vitamin deficiencies
in those with alcohol addiction, largely thought to be due to having a poor diet. This can lead to problems like Wernicke–Korsakoff
syndrome which results from thiamine deficiency in chronic users of alcohol, and causes problems
like vision changes, ataxia, which is a problem with movement and balance, and an impaired
memory. Excessive alcohol use can also end a person’s
life in an overdose, most often due to severe cardiac and respiratory depression, to the
point where a person may lose consciousness and simply stop breathing. For individuals with alcohol use disorder,
the most effective treatment is a combination of individual and group therapy. For example, motivational interviewing is
an individual therapy that can be used to understand why an individual wants to stop
using alcohol and identify specific barriers to treatment. Cognitive-behavioral therapy can help an individual
learn about withdrawal, discuss the thoughts, feelings, and behaviors that lead to alcohol
use, and create a plan to navigate triggers for use. In addition to individual therapies, peer-support
programs that use group discussions to help individuals commit to ending the use of alcohol
as well as provide a space to hold each other accountable and build up their support groups. There are also medications for alcohol dependence,
including naltrexone, acamprosate, and disulfiram, which work best in conjunction with therapy. Naltrexone is a mu-opioid receptor antagonist
that blocks the euphoric effects of alcohol and feelings of intoxication. This can help people with alcohol use disorder
reduce heavy drinking enough so that they stay motivated to continue treatment and avoid
relapse. Acamprosate can be administered immediately
following acute withdrawal, and reestablishes some of the GABA and glutamate pathways that
are disrupted by alcohol. Finally, there’s disulfiram, which works
by inhibiting the enzyme acetaldehyde dehydrogenase. In the body, alcohol is converted to acetaldehyde,
which is then broken down by aldehyde dehydrogenase. So when acetaldehyde dehydrogenase is inhibited,
acetaldehyde levels build up and cause the effects of a “hangover” to happen immediately
after alcohol is consumed, which decreases the likelihood that a person will drink alcohol
again. All right, as a quick recap, alcohol consumption
affects different neurotransmitters and neural systems in the brain, which produces impairment
that is initially pleasant or enjoyable, but can become more problematic and unpleasant
if drinking continues. Long-term use can cause tolerance which is
the need for increasing doses to achieve the same effect, as well as dependence which is
the reliance on the alcohol to function normally. The most effective treatments can include
a combination of therapy and medications—with a lot of love and support from family and
friends. Thanks for watching, you can help support
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