David Cohen, M.D.·Published 27 September 2008·9 min read
Key points
It probably first appeared in skins full of grape juice that had been left out too long in the heat of the desert.
Fruit syrup plus heat (and a few other ingredients) eventually produce ethanol, which is the active ingredient in all types of intoxicating beverages.
Alcohol is found in beer, wine, and distilled spirits.
The differences among these beverages is in the concentration of the alcohol.
The six large groups of mood-altering drugs are alcohol (beer, wine, distilled spirits), depressants (barbiturates, tranquilizers, sedatives, sleeping pills), stimulants (cocaine, amphetamines, caffeine, nicotine), opiates (heroin, opium, morphine, synthetic morphine compounds), hallucinogens (marijuana, LSD, PCP), and inhalants (nitrous oxide, toluene, gasoline).
Alcohol
Alcohol has been around for centuries. It probably first appeared in skins full of grape juice that had been left out too long in the heat of the desert. Fruit syrup plus heat (and a few other ingredients) eventually produce ethanol, which is the active ingredient in all types of intoxicating beverages.
Alcohol is found in beer, wine, and distilled spirits. The active ingredient is the same - ethanol. The differences among these beverages is in the concentration of the alcohol. Beer is the most dilute, and the alcohol content varies from state to state. Wine is a little less dilute, and alcohol contents vary according to the type of wine. Less dilute are the distilled spirits, such as vodka or whiskey. Pure grain alcohol is the least dilute and is the substance known as "moonshine" or "corn squeezings."
Alcohol dissolves fat. The cells in our bodies are encased in membranes, which are complicated multilayered structures composed of specialized fats and proteins. They contain channels for various ions, such as calcium and potassium, and for messenger proteins that communicate with other cell structures which regulate the activity of the cell. Alcohol not only dissolves into the fats of the cell membrane but also disrupts many of these delicate structures.
But because it dissolves fat, alcohol crosses easily into all types of cells. This is one reason that drinking on an empty stomach makes a person drunk quickly. If there is nothing in the stomach, the alcohol crosses easily through the stomach lining and into the bloodstream, then through the blood-brain barrier, which is a specialized fatty membrane that protects the brain from many of the substances that get into the bloodstream. While it is exerting its intoxicating effects on the brain, it is also passing into the cells of various other organs in the body. This results in a variety of toxic effects.
What happens when you drink? In the short term, alcohol causes mild stimulation at first. It causes an easing of tension, a mild sense of euphoria, and a slight drop in inhibitions. It is for these effects that alcohol is used in social settings. But these occur only at low blood levels of alcohol.
As blood levels increase, the depressant effects become more obvious. Since alcohol affects the balance center of the brain, you become uncoordinated. Another part of the brain that becomes less functional is the frontal lobe area, which is the one that exercises social judgment. You might begin to make remarks that are inappropriate or do things that will seem embarrassing later. You might become irritable and easily provoked. Speech becomes slurred, and fine motor coordination is lost. Your ability to perform complex tasks such as driving is lost. And your ability to judge whether or not it's appropriate to drive is also lost.
Written and revised by
David Cohen, M.D.
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As blood levels rise further, you may become stuporous and eventually lose consciousness. This is not quite the same as going to sleep, since it is a drug-induced state. The normal patterns of sleep, such as alternating periods of deep sleep and dreaming, are disrupted. At this point, the danger exists of an alcohol-induced coma with total depression of life functions such as the breathing reflex. Far too often we hear about teenagers or young adults who have intentionally drunk to a point of extreme intoxication and have ended up dead from respiratory arrest due to the alcohol.
Because the chemical structure of alcohol is fairly simple, one would expect it to have a number of diverse effects on the brain, and it does. Unlike some other addictive substances, alcohol does not interact directly with specific neurotransmitter systems. But it does interfere with the activity of a number of substances important in the regulation of mood and excitability of the brain. Alcohol also has a cascading effect on several systems in the brain, probably produced in part by the effects that it has on the fats within the membranes of nerve cells. Each of these intoxicating effects reflects alcohol's interaction with and disruption of a different brain system. We can break down the intoxicating effect of alcohol on the brain into four basic categories: mood-altering effects, motor impairment, interference with memory, reasoning, and judgment, and addictive potential.
The research literature on the molecular effects of alcohol is very complicated, so we'll just touch the high points. {pagebreak}
Alcohol has been found to cause short-term and long-term changes in a number of chemical systems, including those of the neurotransmitters GABA (gamma amino butyric acid), norepinephrine, serotonin, dopamine, adenosine, and choline.
Changes in these systems are felt to account for most of alcohol's intoxicating effects. The addictive potential of alcohol arises from two sources.
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As the brain adapts to the substance's widespread intoxicating effects, it adjusts its internal regulating systems to compensate.
So when you stop drinking, you experience some very unpleasant sensations, including anxiety, depression, shakiness, inability to sleep, and irritability. Drinking alcohol again brings the system back into equilibrium - for a while. It is reinforcing, then, to drink again, and the cycle continues. It was initially thought that this was the basis of addiction to alcohol - drinking to avoid the effects of withdrawal. But it goes further than that.
As we have learned, addicting drugs interact at some point within the ventral tegmentum or medial forebrain bundle, structures that make up the pleasure center of the brain. Several lines of evidence suggest that alcohol has an effect, probably indirectly, on the dopamine system in this part of the brain. Research indicates that there may be genetic differences in the sensitivity of the dopamine system to alcohol. Evidence also exists that alcohol affects the opiate system of the brain. The suggestion is that there may be genetic differences in play here, too.
The research so far supports the long-standing observation that there appear to be different types of alcoholics. Some alcoholics seem to be as highly addicted to alcohol as heroin or crack addicts are to their drugs of choice. Others have less craving when dry, but lose control of the amount they drink.
Genetic differences in how the brain responds to the effects of alcohol might explain this difference.
Longer-term effects of alcohol fall into two categories: adaptive changes in the brain and direct toxicity. As we saw in the section on tolerance, the brain adapts to the presence of a mood-altering drug by trying to bring the system back into equilibrium. With alcohol, the overall effect is to crank up the brain's alerting system so that a person can have more alcohol in his or her system without experiencing the depressant effects. Over the long term, this leads to a situation that we call chronic withdrawal, which means that the whole central nervous system remains hyperactive even if the person is drinking on a regular basis. It is even possible for someone with severe alcoholism to begin to have the symptoms of DTs (delirium tremens) with alcohol still in the system. Alcoholics commonly have generalized seizures while drinking heavily due to this hyperactivity and oversensitivity of the central nervous system.
Other symptoms of chronic withdrawal (or the long-term adaptation of the brain to the presence of alcohol) can be both physical and psychological. High blood pressure is a common physical manifestation, as are chronic sinus congestion and a low-grade tremor. People dependent on alcohol also complain of a variety of psychological symptoms including irritability, anxiety, panic attacks, depression, mood swings, and paranoia. These symptoms reflect the long-term adaptation of the brain to the presence of alcohol and eventually clear with abstinence. Most symptoms are markedly better within two weeks of detoxification, although some emotional instability may remain for several months.{pagebreak}
Although alcohol is legally produced, sold, and used in our society, it is one of the most toxic substances on our list of addictive drugs. It is toxic to several organ systems in the body, including the liver, bone marrow, brain, heart, stomach lining, and pancreas.
When alcohol is metabolized in the liver, it causes a general inflammation, which leads to the development of fatty deposits in liver cells. Over time, with repeated inflammation due to alcohol, some people develop scarring in the liver, which leads to cirrhosis. The word "cirrhosis" literally means "scarring." As these scars form between liver cells, the liver contracts and becomes hardened, resulting in a reduced ability of the liver to perform its function of clearing wastes from the system. It also blocks the flow of blood through the liver. Blood in the large veins coming out of the abdomen starts to back up, resembling a clogged drainage system. This results in symptoms such as hemorrhoids or fluid collection in the abdomen. Over the long term, bulging areas occur in large veins in such places as the esophagus, and these can rupture, leading to serious hemorrhage. The liver also produces important clotting factors, and a damaged liver leads to problems with slow blood clotting. A hemorrhage in this situation is very serious. Since the liver is not clearing wastes, a build-up of ammonia can occur in the blood-stream, leading to inflammation of the brain and decreased consciousness.
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Alcohol is toxic to the bone marrow as well. The cells that are the forerunners of mature blood cells are damaged, and larger, less mature red blood cells are released into the system. Alcohol also damages the immune system, with the result that alcoholics are more prone to a variety of serious infections. Alcohol has several specific toxic effects on the brain.
Many alcoholics become deficient in vitamin B-1, or thiamine.
A part of the brain that is important in the processing and storing of memory is particularly sensitive to the combined effect of the vitamin deficiency and the presence of alcohol.
When this part of the brain is destroyed, it causes the person to lose the capacity to retain any new information. Alcohol also is destructive to the cerebellum, the part of the brain that controls balance and muscle movement. In some individuals, the part of the brain that connects the two hemispheres is also damaged, and there seems to be a hereditary disposition to this type of brain damage. Some alcoholics develop auditory hallucinations, which are voices that are usually derisive and unpleasant. This also seems to be due to brain damage caused by the alcohol. And, in addition, alcohol causes generalized damage to all nerve cells, which can lead to dementia, or loss of intellectual functioning. This can be quite severe, rendering the person in need of supervised institutional care.
Alcohol damages muscle tissue, which is most serious when the damage occurs to the heart muscle. Alcoholic cardiomyopathy is a condition in which the heart muscle has been damaged, and is flabby and dilated. When the heart does not pump effectively, heart failure results. Also, the heart beats in an uncoordinated fashion, compounding the problem.
Alcohol is toxic as well to the lining of the stomach and the digestive tract. It is not uncommon for people to have acute gastritis (irritation of the stomach) following a drinking binge. This can cause pinpoint bleeding, which results in vomiting, diarrhea, and anemia. If this happens in a person with cirrhosis, it can result in a disastrous gastrointestinal hemorrhage.
Alcohol irritates the pancreas, an organ lying beneath the stomach across from the liver. Its function is to produce digestive enzymes and insulin. When it is inflamed, it releases its digestive enzymes and begins to destroy itself. This is a very painful condition. Furthermore, repeated episodes of pancreatic inflammation eventually damage the cells that make insulin. Without insulin, the body cannot control blood sugar, and this causes a diabetic condition.
Alcohol, which is socially acceptable and legal in most countries, is one of the most toxic of the addictive drugs to all body systems. Even social drinkers, who do not develop addiction to alcohol, are not immune to its toxicity.
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