Effects of Alcohol : Neurochemical, Physiologic

In this blog, we will read about the effects of alcohol on the human body. 

Alcohol’s Effect On The Brain 

There can be neurochemical, behavioral, sleep, and other CNS effects on the brain due to alcohol. 

1. Neurochemical Effects of Alcohol On the Brain
   • Alcohol affects almost all neurotransmitter systems.
   • The most potent effect of alcohol is on ?-aminobutyric acid (GABA), especially the GABA-A receptor. 
   • It leads to various effects such as sedation, sleep-inducing properties, anticonvulsants, and muscle relaxation. 
   • These effects vary in the intoxicated state and withdrawal state. The effects of withdrawal are opposite to intoxication effects. 
   • GABA is produced in the body of a  Person taking alcohol and sudden withdrawal leads to excitation. The symptoms of withdrawal occur due to a decrease in neurotransmitters such as GABA.  
   • Glutamate-gated ionophoric receptors, especially n-methyl D aspartate (NMDA), are excitatory receptors.
   • In intoxication, there is a decrease in stimulatory effects, and during withdrawal, it has increased activity. 
   • In acute alcohol consumption, there is an increase in dopamine and its metabolites.
   • Whereas, in chronic use, there are changes in dopamine receptor numbers and sensitivity with effects on intoxication and cravings related to changes in pleasure centers in the ventral tegmental area (VTA).  
   • There is an increase of serotonin in synapse and upregulation of serotonin receptors on alcohol consumption.
   • Lower brain 5HT levels are associated with a less intense response to alcohol and consuming more alcohol per occasion. 
   • Other systems are also affected. There is acutely increased functioning of the opioid-related brain system.  
   • It also impacts adenosine, acetylcholine, and cannabinoid-1 (CB1) receptors.
2. Behavioral Effects of Alcohol On the Brain
   • After alcohol consumption, one may feel euphoric for some time due to decreasing inhibitions, but it is a CNS depressant. It produces somnolence and decreases neuronal activity.  It is not powerful in attenuating pain. 
3. Effects of Alcohol on Sleep
   • People consuming alcohol have problems related to sleep. Although alcohol consumed in the evening increases the ease of falling asleep i.e. decreases sleep latency. Alcohol has adverse effects on sleep architecture. It decreases REM sleep and deep sleep. It has more sleep fragmentation with more and longer episodes of awakening with more intense and disturbing dreams in late night as blood alcohol levels fall.
4. Other CNS Effects
   • Alcohol can cause cerebellar degeneration.
   • Due to a combination of effects of ethanol, acetaldehyde, and vitamin deficiencies, symptoms such as unsteady gait, impaired standing steadiness, and nystagmus are seen.
   • This is treated with total abstinence and vitamin supplementation.   
   • Complete recovery may not be seen in all the patients.
   • Thiamine or vitamin b12 deficiency is also seen in chronic alcohol use patients. 
   • Thiamine deficiency can lead to neurocognitive disorders such as Wernicke's encephalopathy and Korsakoff's syndrome. 
   • 10% of people with AUD may have peripheral neuropathy. There is a deterioration of the functioning of nerves in the hands and feet. 
   • There may be symptoms of numbness of hands and feet often bilateral with tingling and paresthesias. 
   • It is usually mild and improves on abstinence, but in some patients, the pain and numbness may be permanent.  

Other Physiologic Effects of Alcohol

The most significant adverse effects of alcohol use are related to liver damage. The use of alcohol may lead to fatty liver, a reversible swelling of the liver caused by the accumulation of fats and proteins in cells. 

1. Effect of Alcohol on the Liver

Alcoholic hepatitis can be a result of chronic alcohol use. It is inflammation of liver cells with increased liver function tests.  Liver cirrhosis is seen in 15% of patients with AUD where there is scarring of the liver. Subsequent liver failure can cause cognitive impairment and hepatic encephalopathy. 

 2. Effect of Alcohol on the Gastrointestinal Tract

• The gastrointestinal system is affected due to heavy drinking. 
• Patients may have esophagitis, gastritis, and gastric ulcer disease. There may be acute or severe inflammation with vomiting and bleeding. 
• Patients who develop cirrhosis may have dilated esophageal veins. If these patients develop vomiting, it can lead to excessive blood loss. 
• Heavy drinking also negatively affects food digestion and absorption. 
• It inhibits the intestine’s capacity to absorb nutrients like vitamins and amino acids and leads to vitamin deficiencies, especially vitamin B. 
• Pancreatitis is seen in 10% of patients with AUD. 
• Acute pancreatitis can lead to chronic, irreversible conditions with impaired sugar metabolism and lead to a form of diabetes as well.   
• Pancreatic cancers can also be developed. 

3. Effect of Alcohol on the Cardiovascular System

• Heavy alcohol intake and withdrawal symptoms may lead to increased blood pressure, LDL cholesterol, and triglycerides and an increased risk of myocardial infarction, thrombosis, and cardiovascular diseases. 
• Alcohol at high doses acts as a striated muscle toxin.
• It deteriorates heart muscles and subsequently leads to alcoholic cardiomyopathy. These patients have irregular heartbeats and signs of heart failure. 

4. Effect of Alcohol on the Hematological System

In patients who consume 4-8 drinks or more per day, there is a decrease in WBC production and cell ability to mitigate the infection site. This can affect stem cells, leading to an increased average size of RBCs ( MCV) and impairing blood platelet production. 

5. Effect of Alcohol on the Cancer

• Alcohol use disorders are associated with increased rates of most cancers, especially head, neck, esophagus, stomach, liver, colon, lungs, and breasts. 
• Possible causes of cancer in these patients may be alcohol-related immunosuppression or direct effects of ethanol and acetaldehyde on the mucosal membranes. 
• Cancer is the 2nd most common cause of death associated with AUDs. 

Effects of Alcohol On Fetus

• Pregnant women consuming alcohol have devastating effects on the fetus.  
• Women with alcohol-related disorders have a 35% risk of having a child with defects. 
• When the woman consumes alcohol or acetaldehyde, it crosses the placenta and at high doses, it can cause fetal death and spontaneous abortion.  
• At Least 5% of surviving infants of mothers drinking heavily lead to fetal alcohol syndrome. 
• Findings of fetal alcohol syndromes are irreversible. The patient may have a low IQ, small head, low birth weight, atrial septal defect, and syndactyly. 
• Fetal alcohol syndrome is the leading cause of intellectual disability in the USA. 
• It can also lead to facial abnormalities such as a flat bridge of the nose, absent filtrum, and epicanthic eye folds. 
• Additional less obvious findings in fetal alcohol spectrum disorders (FASD) are mild to moderate cognitive difficulties such as impaired executive functioning and difficulty with impulse control etc.
• There may be an increased risk of substance use disorders in children born with fetal alcohol syndrome.

Other Problems Associated with Use of Alcohol

• Testicular atrophy is seen in males. 
• In women, alcohol intake increases estradiol in the blood. It correlates with blood alcohol levels.  
• Other problems related to alcohol may be bone fractures, muscle weakness, eye problems like cataracts, dental problems, skeletal muscle wasting, and increased risk for accidents. 
• Acute intoxication may be associated with hypoglycemia and if unrecognized can cause sudden death. 

Frequently Asked Questions

Question: How does alcohol affect REM sleep?

A. Increases REM sleep

B. Decreases REM sleep

C. Does not affect REM sleep

D. Stabilizes REM sleep

Answer: B. Decreases REM sleep

Question: What symptoms may be seen due to cerebellar degeneration caused by alcohol?

A. Hypertension

B. Unsteady gait and impaired standing steadiness

C. Respiratory depression

D. Hyperactivity

Answer: B. Unsteady gait and impaired standing steadiness

Question: In what percentage of patients with Alcohol Use Disorder (AUD) is liver cirrhosis seen?

A. 5%

B. 10%

C. 15%

D. 20%

Answer: C. 15%

Question: What is the leading cause of intellectual disability associated with alcohol use during pregnancy?

A. Down syndrome

B. Fetal alcohol syndrome

C. Cerebral palsy

D. Autism spectrum disorder

Answer: B. Fetal alcohol syndrome

Question: What physiological change is seen in males due to heavy alcohol intake?

A. Increased testosterone levels

B. Testicular hypertrophy

C. Testicular atrophy

D. Enhanced fertility

Answer: C. Testicular atrophy

Question: In chronic alcohol use, what changes occur in dopamine receptor numbers and sensitivity?

A. Decreased dopamine production

B. Unchanged dopamine receptor numbers

C. Increased dopamine receptor numbers and sensitivity

D. No effect on dopamine receptors

Answer: C. Increased dopamine receptor numbers and sensitivity

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