shown to cause chronic inflammation of the
6.2 Alcohol and body systems. Once consumed,
esophagus, which can lead to esophageal cancer.
alcohol enters the bloodstream and becomes dis-
During swallowing, the esophagus contracts and
tributed throughout the body. Although heavy
relaxes to help food reach the stomach. By inhibit-
drinking is most commonly associated with liver
ing this contraction, alcohol allows acidic stom-
damage, it can also affect the digestive, cardiovas-
ach juices to back up into the lower esophagus.
cular, immune, and endocrine systems.
The presence of stomach acids in the esophagus
The liver. Excessive drinking can harm nearly
can lead to inflammation, ranging from mild to
every organ in the body; however, it is most com-
severe. Long-term exposure to stomach acid can
monly associated with liver damage. The liver is
cause the cells lining the esophagus to progress
especially sensitive to the effects of alcohol
toward esophageal cancer. Heavy alcohol use has
because it receives blood directly from the intes-
also been linked to pancreatitis (inflammation of
tines, the major site of alcohol absorption. The
the pancreas) and cancers in various other body
liver is the primary site of alcohol metabolism, yet
parts, including the mouth, throat, breast, colon,
a number of the byproducts of this metabolism are
and rectum.
toxic to the liver itself. Accumulation of these
Although drinking alcohol is not specifically asso-
byproducts leads to alcohol-induced liver damage,
ciated with increased risk for stomach cancer, it
which can take the form of either inflammation
may be involved in gastritis (inflammation of the
(alcoholic hepatitis) or liver scarring (fibrosis or stomach). A bacterium called Helicobacter pylori
cirrhosis). Often both types of damage exist
( H. pylori) has been shown to cause gastritis and
within the same person. Alcohol abuse is the lead-
stomach ulcers; heavy drinkers have higher rates
ing cause of liver-related deaths in the United
of gastritis and H. pylori infection than do light
States. It is estimated that over 2 million people
drinkers. Since gastritis among alcoholics is not
suffer from some form of alcoholic liver disease.17
reduced by stopping drinking, but rather by treat-
The mechanisms by which alcohol damages the
ment with antibiotics, it may be the bacterial infec-
liver are complex and incompletely understood.
tion rather than the alcohol that causes gastritis.
35
Information about Alcohol
Understanding Alcohol: Investigations into Biology and Behavior However, heavy alcohol use may increase suscepti-hypertension. One proposed mechanisim involves
bility to gastritis. Scientists currently are investi-
changes in the levels of various hormones and
gating whether the higher rate of gastritis among
neurotransmitters that regulate cardiac function.
heavy drinkers is due to alcohol or to H. pylori
Another proposed mechanism states that alcohol
infection.
interferes with the ability of muscles in the arteries
to contract. Alcohol-induced hypertension is not
The cardiovascular system. At high concentrations,
permanent, and among heavy drinkers, it disap-
alcohol can interfere with the pumping action of
pears within two or three weeks after drinking
the heart. Its effects can be acute or chronic. Alco-
stops. The long-term presence of alcohol-induced
hol exerts its effects through a variety of mecha-
hypertension in alcoholics may play a role in the
nisms, including interfering with the sodium-
association between drinking and the risk of
potassium pump (which is needed to move an
stroke.
electrical impulse through the heart) and disturb-
ing the heart’s response to certain hormones. The
Coronary artery disease is the leading cause of
short-term effects of alcohol disturb the electrical
death in Western societies, accounting for about
events that control the contraction of the heart
25 percent of all deaths. Despite the clear associa-
muscle and interfere with the rhythm of the
tion between heavy drinking and heart disease,
heartbeat. These effects are thought to be major
moderate drinking is correlated with reduced risk
reasons for sudden death among alcoholics.
for coronary artery disease.44 Scientists currently
are attempting to establish whether the protection
comes from the alcohol or the lifestyles of moder-
At high concentrations,
ate drinkers. For example, a number of studies
alcohol can interfere with the
suggest that drinking moderate levels of wine pro-
pumping action of the heart.
duces the most protection against coronary heart
disease. The reason for this is not clear. Wine
Long-term effects of heavy drinking may involve
drinkers are also associated with leading healthier
interfering with the action of the energy-produc-
lifestyles than are people who prefer to drink beer
ing parts of the heart cell called mitochondria.
or liquor. This protective effect of moderate alco-
Studies of alcohol-fed hamsters have shown that
hol drinking must be weighed against its
after 14 weeks’ of high BACs, the heart loses some
increased accident risk. These benefits are also
of its ability to beat properly. This effect was
offset at higher drinking levels due to increased
accompanied by a lower-than-normal energy out-
risks of other types of disease and traumas.
put from the mitochondria.54 When hamsters,
The immune system. It is well documented that
which have life spans of approximately three
people who drink heavily suffer more infectious
years, were given longer exposures to high BACs,
diseases than do people who only drink moder-
they were able to bring the energy output of their
ately. For example, various studies have found
mitochondria back to normal, but their hearts still
that drug and alcohol abusers are infected by the
didn’t beat as well as they normally do. This study
bacterium that causes tuberculosis at a rate that is
suggests that the body’s adaptive response to long-
15 to 200 times greater than that of nonabusers.
term alcohol use is unable to fully restore normal
Today, we know that alcohol abuse can alter the
heart function.
distribution and function of immune cells called
Hypertension (high blood pressure), strongly
lymphocytes by interfering with molecules called
associated with drinking more than four drinks
cytokines that help orchestrate lymphocyte activ-
per day, can be another result of long-term alcohol
ities. Alcohol can increase cytokine production in
use. Several mechanisms have been proposed to
liver cells, which leads to the scar formation and
explain the relationship between drinking and
impaired blood flow associated with cirrhosis. In
36
turn, abnormal cytokine concentrations can lead
The short-term behavioral effects of alcohol fol-
to a poorly regulated immune system that is less
low the typical dose-response relationship charac-
capable of fighting off infections.
teristic of a drug; that is, the greater the dose, the
greater the effect [see 5.2 Measurement of blood
Alcohol’s effects on the immune system can be even
alcohol concentration (BAC)]. Table 4 shows that
more severe. If alcohol damages the immune sys-
increased blood alcohol concentrations lead to
tem to a level where it fails to accurately distinguish
changes in personality as well as loss of control
self from nonself, the immune system attacks the
over physical functions. An early (and nearly uni-
body. This can result in, or worsen, alcohol-
versal) effect of alcohol on personality is the loss
induced organ damage such as alcohol liver dis-
of inhibition. Other effects experienced at lower
ease. Regrettably, children born with fetal alcohol
BACs (0.01–0.05) include a sense of well being
syndrome (FAS) must cope with the effects of alco-and lowered alertness. These BAC values also
hol on their immune systems throughout their lives
impair thought, judgment, coordination, and con-
(see 10.4 Drinking and pregnancy and Table 4). FAS
centration in most individuals.
results from alcohol consumption by pregnant
women. Prenatal exposure to alcohol can disrupt
the normal formation of the fetal immune system,
The short-term behavioral effects of
leading to increased frequencies of infection and an
alcohol follow the typical dose-response
increased risk of organ damage, among other
relationship characteristic of a
adverse, lifelong effects.
drug; that is, the greater the dose,
The endocrine system. Long-term alcohol use can
the greater the effect.
also disrupt the function of the endocrine system
and affect the balance of the hormones insulin
and glucagon, which regulate blood glucose con-
It is easier to predict the physical effects of alcohol
centrations. Drinking alcohol can alter the release
than the behavioral ones, especially at BACs in the
of reproductive hormones, growth hormone, and
range of 0.06–0.20. Personality influences behav-
testosterone. Alcohol-induced changes in hor-
ioral responses. Loss of inhibition combined with
mone concentrations are associated with sexual
additional drinking leads some individuals to
dysfunction in both men and women. Alcoholics
become increasingly boisterous while others
also face increased risk of osteoporosis. The dis-
become withdrawn. Still others become angry and
ruption of certain hormones, such as parathyroid
aggressive. Not surprisingly, inappropriate expres-
hormone, vitamin D–related hormones, and calci-
sion of anger and aggression can lead to abusive
tonin, may lead to a calcium deficiency.
behavior and violence (see 10.5 Drinking and vio-
lence). Excessive drinking may also cause some
7 Alcohol: Behavioral Effects
individuals to experience severe emotional swings
The brain is the origin of all human behavior, so it
and even trigger severe depression. At BACs of
is not surprising that exposure to alcohol leads to
0.21–0.29, loss of muscle control leads most indi-
changes in behavior. As discussed in 6.1 Alcohol and
viduals to experience stupor and impaired sensa-
the brain, the human brain has a high water content.
tions. Since BACs over 0.30 affect breathing and
Consequently, it is very sensitive to the effects of
heart rate, all individuals experiencing this BAC
alcohol consumption. Alcohol induces several
are at risk for unconsciousness, coma, and even
behavioral changes because it affects various areas of
death.
the brain. For example, the cerebellum (move-
ment), the hippocampus (memory), the ventral
Though the behavioral effects of alcohol are unpre-
tegmental area (reward), and even the brainstem
dictable and vary from one individual to another, a
(breathing) are all affected by drinking alcohol.
number of factors are known to influence alcohol’s
37
Information about Alcohol
Understanding Alcohol: Investigations into Biology and Behavior Table 4. Progressive Effects of Alcohol
effects on behavior. One important factor that influ-
decide whether the choice to drink alcohol would
ences both personality and susceptibility to alcohol
be risky.
abuse is genetics (see 8.2 Alcoholism and genetics,
on page 39). Genetic influences work at both the
Drinkers expect to feel and behave in
individual and the population levels. For example,
certain ways when drinking. Expecta-
certain genetic variations that exist more often in
tions about drinking can begin at an
Chinese and Japanese populations lead to an
early age, even before drinking begins.
increased sensitivity to alcohol’s effects, which in
turn leads to a decreased susceptibility to alco-
holism. An individual possessing these genetic vari-
There are, of course, nongenetic factors that influ-
ations experiences facial flushing, an elevated heart
ence drinking behavior. The term expectancy
rate, and a burning sensation in the stomach upon
refers to what a person expects will happen in a
consumption of alcohol. These negative conse-
given drinking situation. Research has shown that
quences generally deter further alcohol consump-
drinkers expect to feel and behave in certain ways
tion. In other populations, different genetic
when drinking. Expectations about drinking can
variations lead to an increased susceptibility to
begin at an early age, even before drinking
alcoholism. In still other populations, genetics has
begins.48 Students who engage in binge drinking
not been shown to influence an individual’s drink-
during high school are more likely to do so in col-
ing behavior. It is important to remember that an
lege.57 Young people are also influenced by their
individual cannot control his or her genetic
perceptions of how much they think their friends
makeup, but being aware of it can help a person
drink. Studies have shown that college students
38
tend to think their friends drink more than they
holism. More recently, the diagnostic criteria have
actually do.40 This belief can cause them to
relied more on data and research. Today,
increase their level of drinking in an effort to “fit
researchers and clinicians in the United States rely
in.” Other social factors that promote increased
on the Diagnostic and Statistical Manual of Mental
alcohol consumption are drinking in groups and
Disorders (DSM) published by the American Psy-
serving oneself.20, 21
chiatric Association.1 The DSM recognizes separate
criteria for the diagnosis of alcohol dependence
8 Alcoholism
(alcoholism) and alcohol abuse.
8.1 Signs of a problem. There is no simple test to
8.2 Alcoholism and genetics. Most people who use identify someone with a drinking problem. How-alcohol do so without problems. However, about
ever, clinicians often use a short series of ques-
17 percent of current regular drinkers either abuse
tions as a screening tool. Honest answers to the
it or are dependent on it. Regular drinkers are
following four questions can help individuals
defined as those who have consumed 12 or more
decide whether a problem may exist. To make the
drinks in the past year. An individual’s suscepti-
questions easier to remember, they have been
bility to alcoholism is influenced by many factors.
written in such a way that the first letter of a key
Scientists believe that, among other factors, there
word in each question spells CAGE.41
is a genetic basis for alcoholism because children
1. Have you ever felt that you should cut
or siblings of alcoholics are at much greater risk
down on your drinking?
for developing the disease.
2. Have people annoyed you by criticizing
It is important to keep in mind that members of
your drinking?
the same family share both genes and a common
3. Have you ever felt bad or guilty about your
environment. To distinguish between the effects
drinking?
of nature versus nurture, scientists have con-
4. Have you ever had a drink first thing in the
ducted twin and adoption studies. Identical twins
morning to steady your nerves or to get rid
have the same set of genes. In contrast, fraternal
of a hangover (eye opener)?
twins, like nontwin siblings, share an average of
A “yes” answer to one of these questions may sug-
half their genes. Thus, both types of twins share
gest that a drinking problem exists, while more
environmental influences to a similar degree, but
than one “yes” response is highly indicative of a
they differ in the amount of genetic information
problem. Even if a person answers “no” to all four
they share. If a trait shows greater similarity
questions, an alcohol problem can still exist. If the
among identical twins compared with fraternal
screening procedure suggests that an alcohol-
twins, then genes contribute to that trait.
abuse or alcohol-dependence problem may exist,
then that individual should be further evaluated
Children who are adopted at an early age provide
by a qualified healthcare provider.
an opportunity to separate genetic from environ-
mental effects. The assumption is that any simi-
larities for a trait between biological parents and
Most people who use alcohol do so
their adopted-away offspring are due to genetics.
without problems. However, about
Conversely, similarities between adoptive parents
17 percent of alcohol users either
and their adopted children reflect shared environ-
abuse it or are dependent on it.
mental influences. Twin and adoption studies
indicate that there are strong genetic influences on
The criteria used by healthcare providers to diag-
alcoholism. It is important to stress, however, that
nose alcohol abuse and alcoholism continue to be
many individuals who are genetically predis-
refined. Prior to the 1970s, subjective judgments
posed to become an alcoholic do not do so.
and clinical experience were used to diagnose alco-
Genetic influence speaks to an individual’s risk,
39
Information about Alcohol
Understanding Alcohol: Investigations into Biology and Behavior not their destiny. The environment, including the
person who drinks alcohol while taking disulfi-
social setting of the individual, is a very important
ram will experience severe discomfort and illness
factor. The individual must engage in the behavior
or, in extreme cases, even death. The expectation
of drinking before the genetic predisposition can
of illness deters the ingestion of alcohol. Often,
set the stage for alcoholism to develop.
however, alcohol abusers do not take the medica-
tion, or take it but continue to drink despite the
The genetic influence on alcoholism is described
consequences. Moreover, disulfiram treats only
as being polygenic, meaning that there is more
the effects, but not the causes, of the disease. This
than one gene influencing the trait. Scientific
reduces its effectiveness unless used in conjunc-
research has identified regions on many chromo-
tion with other behavioral therapies.
somes (1, 2, 3, 4, 7, 11, 15, and 16) that may pre-
dispose an individual to alcoholism . 16, 18, 32, 50 In addition, other regions on chromosome 4 may
help protect an individual from alcoholism. One
such region is near the location of the genes for
the ADH enzyme (see “The cardiovascular sys-
tem,” on page 36). This is especially interesting
because certain alleles, or versions of the ADH
gene, have been shown to reduce the risk for
alcoholism in Chinese and Japanese populations.
Individuals having the ADH2 and ADH3 alleles produce enzymes that metabolize alcohol to
acetaldehyde at a high rate. The accumulation of
toxic acetaldehyde can cause facial flushing, an
Figure 13. Disulfiram is a drug approved by the
elevated heart rate, and a burning sensation in the
Food and Drug Administration to treat alcoholism.
stomach. These negative effects of alcohol con-
sumption are responsible for the reduced rates of
More recently, the drug naltrexone has been
alcoholism among people with these genotypes.
approved as a pharmacological agent to help a
person maintain sobriety.58 Endorphins are
8.3 Alcoholism treatments. Although it is a
among the hormones believed to be involved in
chronic disease, alcoholism can be treated suc-
alcohol craving. Naltrexone blocks the receptors
cessfully. Any successful physiological treatment
for endorphins, thus helping reduce the desire for
for alcoholism must also include a psychological
alcohol. Although clinical trials of naltrexone
component. Similar to other chronic diseases,
have been promising, the drug must be taken con-
such as heart disease or diabetes, relapse is com-
sistently to be effective. This drug should be used
mon during the course of alcoholism. Thus, suc-
in conjunction with psychosocial therapies.
cessful treatment is defined in terms of recovery,
Research is now under way to identify other med-
not cure. Research continues to develop both
ications that can be used alone, or in combination
pharmacological and psychosocial (behavioral)
with other medications, to treat alcoholism.
therapies for alcoholism.54
Individual-initiated (or “self-help”) therapies have
traditionally been the backbone of alcohol recovery.
Any successful physiological treatment
The first such program, Alcoholics Anonymous
for alcoholism must also include
(AA), describes