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Immune System
[Lexile: 1200L]
The invisible battle goes on day and night. There are many enemies lurking
about, waiting to attack. On guard is a tireless army of defenders, posed and
ready to fight. These defenders are part of the immune system--a remarkable
system that protects the body from harmful invasions by foreign substances and
disease-causing organisms.
Immunity
The body's ability to protect and defend itself against a foreign enemy agent is
called immunity. There are several types of immunity. Natural immunity is a
type of general inherited protection. A person is born with natural immunity, and it
is species specific--for example, people do not get cat distemper and cats do not
get human colds. Active immunity is the protection a person develops during
his or her lifetime as the result of actually having been immunized against a
disease. One way this can be done is by using vaccines to help an individual
develop active immunity. Active immunity is long-lived and may even last a
person's lifetime. Passive immunity is a temporary form of immunity that is
borrowed from another source. It is short-lived, only lasting a matter of weeks. A
baby receives passive immunity from its mother before it is born and after it is
born from the mother's milk. Passive immunity protects the baby until it is old
enough to have its "baby shots." Then the baby will build its own active immunity.
When the immune system sets up an attack against a foreign agent, it must first
recognize which cells belong to the body and which do not so that it can
selectively destroy the invader while protecting the healthy body cells. The
immune system can tell the difference between what is self (the body's cells and
tissue) from something that is foreign because of the chemical labels that appear
on the outside surface of all body cells. The cells in a person's body have
chemical self labels; each person has their own unique set of self labels.
Invading agents also have chemical labels; each invading agent has foreign
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antigen labels.
Each foreign antigen has its own chemical configuration--just as each person has
a unique set of human fingerprints. Because each foreign antigen has its own
unique set of chemical fingerprints, the immune system is able to recognize the
difference between foreign agents and develop a separate defense against each.
The Immune Response
The immune response occurs in stages. When an organism invades the body, it
must be recognized as foreign. Once it is recognized, it must be marked so that
all the cells within the immune system will know that it is an invader and is
attacking the body. Then the various troops of immune cells must be called to
battle, a defense plan organized, and the defense begun. Finally, when the
enemy has been defeated, a cease-fire must be sounded and the battle stopped.
Immune Defenses
The immune system has two defense plans: nonspecific and specific. The
nonspecific defense is used against all invaders. Nonspecific responses are
only able to recognize the difference between self cells and foreign antigens. The
response to the foreign antigens occurs quickly and does not require having had
previous encounters with the outside invaders.
In a specific defense, the immune system recognizes the invader as one having
previously attacked the body. Specific immune responses not only recognize self
cells as different from foreign antigens; but they recognize the difference
between the different kinds of foreign antigens.
Immune Cells and Molecules
The cells of the immune system fall into three groups: macrophages, natural killer
cells, and lymphocytes. All types of cells are members of the white blood cell
population and have their origin in bone marrow. These defender white cells
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account for one percent of the body's 100 trillion cells.
Macrophages. The macrophages are the first to the battleground and are part of
a nonspecific defense. They swallow up and dispose of enemy agents, dead
cells, and other debris. They are phagocytes, or "cell eaters." Not only do they
ingest foreign substances, but macrophages also process harmful material so
that it can be recognized as dangerous by other immune cells. These phagocytic
cells constantly wander about, patrolling all the areas of the body. They are found
in the bloodstream, tissues, and lymphatic system.
Natural Killer Cells. Natural killer cells are a group of special immune cells that
are able to quickly identify and destroy a large variety of newly formed cancer
cells, virus-infected cells, and fungi. These immune cells are nonspecific in their
attack.
Lymphocytes. The lymphocytes follow the macrophages into battle against
foreign invaders. Unlike the nonspecific macrophages, lymphocytes are part of a
specific immune defense--they are programmed to recognize and destroy
specific enemy agents. For example, one group of lymphocyte defenders is
trained to recognize and protect against measles and another to protect against
chicken pox.
There are two kinds of lymphocytes: T lymphocytes (T cells) and B lymphocytes
(B cells). Although both types of lymphocytes are formed in the bone marrow, the
T cells leave the bone marrow before they are fully developed and travel to the
thymus gland. In the thymus gland, they mature and are programmed in the skills
needed to function as a T cell. The B cells remain in the bone marrow to receive
their B cell programming.
B Cells. When confronted with a specific enemy agent, some B cells are
programmed to produce immune molecules called antibodies that recognize the
chemical fingerprints of the foreign antigen. Each antibody is made up of long
chains of smaller units in a pattern. The smaller units are amino acids, and it is
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their pattern that matches the chemical fingerprints of a specific foreign antigen-much like a lock and key match each other.
Antibodies do not attack the enemy directly. In battle with foreign invaders, some
antibodies may call phagocytic cells to the battleground, mark the enemy so that
it can be recognized and destroyed, or empty out the enemy cell by punching
holes in its surface.
When the enemy agent has been defeated, other B cells store information about
the invader for the future. If the foreign agent invades the body again, these
memory B cells quickly recognize the foreign antigen and signal the production of
antibodies to begin.
T Cells. There are four kinds of T cells: T helper cells, cytotoxic T cells,
suppressor T cells, and memory T cells. The immune response begins with the
command from the T helper cells. They recognize the invader, then call in and
train other immune cells, including B cells and cytotoxic T cells. The cytotoxic
(cell killing) T cells kill the enemy directly. T suppressor cells decide when the
battle ends--they call a truce to the fighting and shut off the immune system.
Memory T cells remain, ready to move quickly should the enemy invade again.
Organ Transplants and the Immune System
Sometimes illness or an accident damages body tissue so much that it is no
longer able to function normally. Then an operation, called a tissue graft, or
transplant, may be performed to replace the damaged part. Healthy tissue, such
as skin, may be taken from one part of the body and grafted to another part of
the body. The body accepts the transplanted tissue because it has the same self
label. Problems arise when the tissue or organs are taken from one person and
transplanted to another. Then the immune system recognizes the transplant as
foreign and launches as attack against it. When this happens, special drugs are
used to lessen the immune system attack.
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Although the body attacks cells that have a different self label, some self labels
are chemically more similar than others and cause less of an immune response.
The self labels are coded by genes inherited from each parent, so brothers and
sisters are more likely to have similar, but not the same, self labels. The only
people who would have the very same self labels would be identical twins,
because they share the same genes.
Disorders of the Immune System
Sometimes the immune system works too hard and an allergic response results
or it mistakes the body's own tissue for an invader and an autoimmune (selfimmune) disease results. Other disorders result when cells in the immune system
are attacked and destroyed by an organism, such as the AIDS virus, which
destroys the T helper cell.
Allergies
Allergies are the result of an overactive immune system. In some people, the
immune system mounts a large-scale attack against common environmental
agents that should pose no threat to the body. Then unnecessary antibodies are
produced against such things as house dust, animal dander, tree and weed
pollens, and in some cases the chemical molecules in certain foods.
Autoimmune Disease
Autoimmune disease is a disorder of mistaken identity. It occurs when the body
has difficulty distinguishing between self and foreign enemies. In rheumatoid
arthritis, for example, the body's immune system acts as though parts of the
knee, hand, or foot joints were foreign enemies, and it attacks them. The reason
that some people develop an autoimmune disease and others do not is unknown.
It is thought that some chemical agent or infectious organism may alter the self
label so that the immune system recognizes certain tissues as enemies.
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AIDS
Acquired immune deficiency syndrome (AIDS) is a disease that destroys the
immune system. AIDS is caused by the human immuno-deficiency virus (HIV).
Like all other viruses, HIV must seek out living cells to infect and in which to
reproduce; it is not able to live on its own. The AIDS virus seeks out the cells of
the immune system, particularly T helper cells and macrophages, to infect.
Eventually the AIDS virus destroys the cell. Without the T helper cell, the immune
system is unable to organize a defense against the invaders. Thus what are
normally harmless organisms can cause life-threatening infections in people who
have AIDS.
Immune Discoveries
Immunology, the study of the immune system, started long ago--even before
people knew there was such a thing as the immune system! By the 1400's there
was a primitive form of immunization. A powder made from dried smallpox scabs
was inhaled as protection against getting smallpox.
Modern immunology really began with the work of two immunologists, the
scientists who study the immune system. It was in 1796 that the first modern
vaccination was developed by Edward Jenner, a physician in England. He
noticed that herdsmen and dairymaids who had been infected with cowpox, a
mild viral disease affecting cows, did not get smallpox. Smallpox was a much
more serious and often fatal disease. He used this information to develop a
method of infecting people with cowpox to protect them from smallpox. The term
vaccination (vacca meaning "cow") was used to describe Jenner's method.
About one hundred years later, the French scientist Louis Pasteur discovered
that chickens infected with a mild form of chicken cholera did not develop the
more serious form of chicken cholera. To infect the chickens, Pasteur developed
a weakened form of the disease-producing organism.
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Since Pasteur's time, vaccines have been developed for many other diseases,
including polio, measles, mumps, tetanus, whooping cough, and influenza. And
methods have been developed to classify different types of blood and tissues,
diagnose cancer, and examine genes and their effect on cell function.
New Weapons for the Future
Vaccines are now used to fight cancer. For example, there is a vaccine that acts
against the virus that causes cervical cancer. Some vaccines act against cancer
cells, such as those in prostate cancer. Another way to fight cancer is to use
monoclonal antibodies. These are laboratory-grown cells that produce huge
amounts of specific antibodies.
In 1988, the first HIV vaccine trial began. In 1999, the HIV Vaccine Trials
Network (HVTN) was formed. In the HVTN, sites around the world test new HIV
vaccines.
And studies are being carried out to assess factors that may affect the immune
system. These factors include diet, exercise, stress, and exposure to pollution.
Carol Mattson Porth
Author, Pathophysiology: Concepts of Altered Health
States
MLA (Modern Language Association) style:
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Porth, Carol Mattson. "Immune System." The New Book of Knowledge®. 2010.
Grolier Online. 15 July 2010 <http://nbk.grolier.com/cgibin/article?assetid=a2014390-h>.
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Allergies
[Lexile: 1000L]
An allergy is an abnormal response by the immune system to a foreign
substance (called an allergen) that is normally harmless. Allergies often begin in
childhood. But they can develop at any time. In the United States, an estimated
50 million people have them.
Symptoms of allergies vary. They can range from mild to severe. The most
common are sneezing, watery eyes, and nasal congestion (allergic rhinitis or hay
fever); breathing difficulties (asthma); and skin rashes.
Other allergy symptoms include itchy and swollen skin (hives), eye inflammation
(conjunctivitis), and digestive disturbances. A rare but severe reaction is
anaphylaxis. It causes swelling of body tissues, breathing difficulties, cramps,
vomiting, and a rapid drop in blood pressure. If not treated immediately,
anaphylaxis can be fatal.
Some allergens, such as pollen, often cause a specific type of allergic response
(hay fever). But other allergens can produce different responses in different
people. For example, an allergy to cat or dog dander may cause hives in one
person and asthma in another.
How Allergies Develop
An allergy develops when the immune system first mistakes a substance that is
harmless for one that is harmful. The immune system is the body's defense
mechanism. It normally responds to harmful substances such as toxins, bacteria,
and viruses. But the immune response can be misdirected.
The immune response involves the production of immunoglobulin E (IgE). This is
an antibody, which is a special kind of protein. IgE antibodies attach themselves
to mast cells (found mainly in the respiratory and digestive system) or to white
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blood cells. When the person is exposed to the same substance again, the
antibodies signal the mast cells or white blood cells to release chemicals that
cause allergic symptoms. Chief among these is a powerful substance called
histamine.
Causes
People can be allergic to many things. However, more are allergic to inhaled
substances than anything else. Of these, the most troublesome are dust and
pollen (fine powders from plants and trees), molds, animal dander, feathers, and
chemicals.
Many people are also allergic to foods such as peanuts, shellfish, and cow's milk,
venom from insects (especially yellow jackets and other wasps and bees), and
drugs such as penicillin.
The most common causes of allergic skin reactions are poison ivy and poison
oak. But many other materials may cause reactions in sensitive individuals.
These materials include latex, soaps, various chemicals, and cosmetics.
A person with a family history of allergies is more likely to develop them than
someone who comes from a nonallergic family. However, it is not the specific
allergy that is inherited, but the tendency to be allergic.
Diagnosis and Treatment
Doctors diagnose most allergies with a physical exam and a skin or blood test. In
a skin test, a small dose of a purified allergen is injected just below the skin, or
lightly scratched into the skin. After a short time, the skin is checked to see if an
allergic reaction (usually redness and swelling) has occurred.
A blood test that detects allergies is called a radioallergosorbent test, or RAST.
For a RAST, a blood sample is taken to measure the amount of IgE antibodies to
one or more possible allergens.
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An allergy cannot be cured. But once it has been identified it can be controlled in
several ways. Avoiding exposure to the allergen is the simplest. Unfortunately,
this is not always possible. It may be easy to avoid certain foods or drugs. But it
is much more difficult to avoid things such as dust or pollen. In such situations,
medications can be used to reduce or eliminate allergic symptoms. These
include antihistamines, anti-inflammatory drugs, and nasal decongestants.
Antihistamines prevent sneezing, watery eyes, and other effects of histamine.
Anti-inflammatory drugs reduce inflammation in the airways. Other medications
are breathed directly into the lungs with an inhaler. These relax the muscles
around the airways to relieve coughing, wheezing, and shortness of breath.
When these methods are not effective, immunotherapy may be recommended.
During immunotherapy, a doctor injects a small amount of the allergen into the
patient's system. Gradually, the amount that is injected is increased. This causes
the immune system to produce less of the antibodies that cause allergic
symptoms. Allergy shots must be given for several years before they work. They
are most effective for allergic rhinitis and allergies caused by insect stings.
Life-threatening allergic reactions are usually treated with injections of
epinephrine. This medication is also known as the hormone adrenaline.
Epinephrine relaxes the muscles in the airways, making it easier to breathe. It
also tightens the blood vessels. It is usually administered by a medical
practitioner. But it can be self injected with a prescription device called an Epipen if medical care is not available.
Adrian M. Casillas, M.D.
UCLA School of Medicine
MLA (Modern Language Association) style:
Casillas, Adrian M. "Allergies." The New Book of Knowledge®. 2010. Grolier
Online. 15 July 2010 <http://nbk.grolier.com/cgi-bin/article?assetid=a2041633-h>.
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Alzheimer's Disease
[Lexile: 900L]
Alzheimer's disease (AD) is a progressive brain disorder. It causes
disorientation, personality changes, and an increasingly severe decline in
memory, thinking, and language skills. It is the most common cause of dementia
(the loss of mental abilities).
AD was first described in 1906 by German physician Alois Alzheimer. It is widely
recognized today. In the United States, an estimated 4.5 million people are
thought to have AD. At least 95 percent of these people have a form called lateonset AD. This form occurs mainly in those aged 65 and older. Risk of late-onset
AD increases with age. Nearly half of people 85 and older have it. But it is not
considered a normal consequence of aging.
Another, less common form of the disease is called early-onset AD. It typically
affects people between the ages of 30 and 60. It accounts for less than 5 percent
of all cases. It is usually inherited and has been linked to mutations in certain
genes.
Early symptoms of Alzheimer's disease usually include forgetfulness, difficulty
finding the right words for things, and subtle personality changes. These
symptoms may be similar to normal signs of aging. As a result, they are often
missed. However, memory declines even further as the disease progresses.
People with AD may routinely forget familiar names and faces. They may
become confused when driving a car or handling money. And they may have
trouble understanding what is being said and may appear to have no interest in
others.
Mood swings are also common, as is increasingly poor judgment. For example, a
person with Alzheimer's disease may wear many layers of clothing on a hot day
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or not enough clothes on a cold day.
During the later stages of the disease, people become even more impaired-mentally and physically. They become bedridden and unable to care for
themselves. This places them at greater risk for other life-threatening illnesses
such as pneumonia. Death usually occurs when deterioration of the brain causes
essential body functions to fail.
The course of the disease varies. The time from the appearance of symptoms to
death ranges from three to twenty years. The average duration is eight years.
Early-onset AD tends to progress more rapidly.
Causes
The brains of people with AD have been found to have two specific types of
abnormal structures. These structures are the physical evidence of AD. But it is
still not known whether they are the primary cause of damage to the brain. Most
experts agree that it is probably a complex set of genetic and nongenetic factors,
rather than a single cause, that triggers the disease process.
Several risk factors are associated with AD. For example, there are the genetic
mutations associated with early-onset AD. Other risk factors include increasing
age, a family history of the disease, and one gene that increases the risk of lateonset AD.
Risk factors for heart disease may also increase the risk for AD. One such risk
factor is high blood pressure. There is also evidence that remaining mentally
active may be associated with a lower risk.
Diagnosis and Treatment
There is no single test to diagnose AD. It is not yet possible to detect the
abnormal structures in the brain while the person is still alive. Instead, doctors
make a diagnosis of "possible" or "probable" AD. This diagnosis is based on tests
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that assess memory and thinking skills. A physical exam is also performed to
exclude other possible reasons for the person's symptoms.
AD has no cure. But scientists are working to develop drugs that prevent or slow
the progression of AD. Some drugs are already available. In some cases, they
may temporarily improve or stabilize memory or thinking skills. Or they may slow
their rate of decline.
Doctors may also prescribe medications to treat symptoms that often affect
people with AD. These symptoms include depression and insomnia. Drug
therapies, as well as various care strategies, can make AD patients more
comfortable and improve their quality of life.
Impact
A diagnosis of AD is usually very difficult for patients and their families. Often,
people with AD are able to live at home and are cared for by a spouse or other
family member. But as the disease progresses, the physical and emotional
demands of home care may become too much for the family. In such cases, the
patient must be placed in an extended-care facility. Support and information for
AD patients and their families is available from organizations. These include the
Alzheimer's Association and various community groups.
Alzheimer's Association
MLA (Modern Language Association) style:
"Alzheimer's Disease." The New Book of Knowledge®. 2010. Grolier Online. 15
July 2010 <http://nbk.grolier.com/cgi-bin/article?assetid=a2000760-h>.
14
People with Disabilities [Lexile: 1080L]
A disability is a permanent condition that significantly limits the kind or amount of
activity a person can perform. The most common are physical disabilities. These
can restrict mobility, use of the hands, and even speaking. Other disabilities,
such as deafness and blindness, affect the senses. Still others are mental,
emotional, or behavioral.
The United Nations estimates that there are some 600 million people with
disabilities in the world today. In the United States, some 36 million people,
roughly one out of every eight, have disabilities. When lesser impairments are
added, the total rises to 56 million people. All people with disabilities also have
abilities. They use these abilities to study, work, support their families, and
contribute to their communities.
Types of Disabilities
In many countries, wars and violent conflicts are a major cause of physical
disabilities in children and adults. Such disabilities can also be caused by
accidents. Or they can be caused by diseases such as cerebral palsy, which
typically occurs at birth. Physical disabilities are most common among senior
citizens and among teens who are injured playing sports or while driving. Most
people with physical disabilities require help to move around.
Physical disabilities related to the senses include problems hearing or seeing.
The term "deafness" is used when a person's hearing loss is severe or profound.
Blindness is defined as 20/200 vision. That is, a blind person can see a letter or a
chart at 20 feet (6 meters) that a typically sighted person can see at 200 feet (60
meters), or ten times 20 feet.
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Blindness and deafness occur most often in people in their 60's or older. But
younger people may become so through accidents or illnesses. Some children
are born blind or deaf (seldom both). Many people who are not blind or deaf may
still have problems seeing or hearing well. They often benefit from hearing aids
and eyeglasses.
Learning disabilities can hamper a person's ability to speak or write, solve
mathematical problems, pay attention, or even understand when other people
speak. Such disabilities are life-long conditions. But most people learn ways to
cope with them. One of the most common types of learning disabilities is a
reading disorder sometimes called dyslexia.
ADHD, a behavioral disorder, is also very common. In one type of ADHD, people
find it hard to pay attention or concentrate. They are easily distracted. In the
other type, they find it hard to sit still, stop talking, or wait their turn.
Mental retardation limits the amount people can learn and how fast they can
learn. Emotional disabilities include mild disturbances and more serious mental
illnesses, such as psychosis, in which a person may lose the ability to deal with
reality.
Other diseases are becoming more common as more people live longer. An
example is Alzheimer's, a disease of the brain. There are also a growing number
of children and young people with autism. Autism is a severe brain disorder that
limits attention, communication, and other interaction with people. To date there
are no cures for either of these diseases.
Prevention and Treatment
Some disabilities can be prevented by early detection, diagnosis, and treatment
of the diseases that lead to them. An example is glaucoma, a disease of the optic
nerve of the eye. It can cause blindness if not treated. Other disabilities can be
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prevented by reducing violence and by cutting back accidents on the road, in the
workplace, and at home.
Proper diagnosis and treatment are critical in aiding people with disabilities.
Almost anyone with disabilities can benefit from rehabilitation. Rehabilitation is
the process of helping people with disabilities make the most of their abilities. It
includes medical care and treatment; counseling; physical therapy; speech and
hearing therapy; self-care and job training; and devices that help people with
disabilities live independently.
For people with physical disabilities, the first step is often medical and surgical
treatment. For example, doctors prescribe digital hearing aids to some patients
with hearing problems so that they may hear better. Many thousands of
Americans who are deaf receive cochlear implants. The implants are surgical
devices that can restore some hearing. Doctors may perform surgery to help
restore sight to some of those who are blind. They may also use a technique
called microsurgery to replace severed limbs. Or they may implant special aids.
These include artificial joints, including hips and knees, to help people walk
again.
Even when abilities cannot be restored surgically, much can be done to help
people with disabilities lead better lives. For example, an occupational therapist
can teach someone who has difficulty walking to use a motorized or manual
wheelchair, crutches, or a walker. With these aids, people with physical
disabilities find it easier to go to school or work or to engage in community
activities. Many products are available that assist people in dressing, eating,
communicating, and other everyday activities. There are more than 100,000 such
devices.
Most people with mental retardation can learn to become less dependent on
others. Through one-on-one instruction, and much practice, people with mild or
moderate mental retardation can often master daily living skills. People with
emotional disorders can be helped with special forms of therapy. They may also
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take medications, which, if taken as directed, alleviate symptoms in many cases.
The most common treatment for people with disabilities is special education. This
type of education uses specially designed teaching materials and methods. For
example, deaf students are taught to read lips and use sign language. Children
with writing disorders may be taught to do their assignments on a computer
keyboard. Or they may take oral rather than written tests. Most people with
ADHD learn to cope with their limitations through special education, along with
supportive treatments.
Increasingly, students with disabilities are benefiting from technologies adapted
for them. For example, children with reading disorders or vision problems can
view words printed in big letters on a computer screen. Or they may have text
read aloud by the computer. For the blind there are Braille keyboards. Those who
have difficulty moving their hands can use a special mouse that does not require
a precise movement to click on an item on the computer screen.
Employment
Some 13 million, or about one-third, of the 36 million American adults with
disabilities have jobs. With education, job training, and modern technology,
people with disabilities can do almost any job their abilities and interests lead
them to try. There are newspaper and magazine writers and editors who are
blind and school and college teachers who are deaf. There are business
executives who have physical limitations and counselors and social workers with
learning disabilities.
Advances in technology are helping people with disabilities to work. For example,
people who are blind use e-mail and word-processing programs that respond to
verbal commands. Those who are deaf make and receive phone calls via highspeed telecommunications connections known as broadband. With broadband,
people may sign to each other over phone lines. Those same broadband
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connections allow people with severe health or mobility problems to
telecommute--that is, to work from their homes.
Role of Government
The United States has laws and programs that demonstrate the role
governments can play in helping people with disabilities. The Rehabilitation Act
of 1973 helps many adults with disabilities get job training. The Individuals with
Disabilities Education Act of 1975 provides special education through high school
for all students with disabilities. The 1990 Americans with Disabilities Act (ADA)
prohibits discrimination against people with disabilities in employment,
transportation, public accommodation, communications, and government
activities.
Largely because of ADA, in most cities and towns in America, people using
wheelchairs or other mobility devices can access public buildings, stores,
recreational facilities, airports, bus terminals, train stations, and other transit
facilities. There is not as much suitable access to private homes and apartments.
The two-thirds of people with disabilities who do not have jobs depend on
government Medicare and Medicaid programs to help pay their medical bills. In
addition, Social Security Disability Insurance and Supplemental Security Income
provide them with some money. People with disabilities cannot use such
programs unless they have little or no job income. Thus, many of them are
discouraged from working.
In addition to the federal regulations cited above, rehabilitation services are
offered in all 50 states through state vocational rehabilitation agencies. Important
support is also provided by private organizations. These include Easter Seals,
United Cerebral Palsy, the American Foundation for the Blind, and the Arc.
On the international level, in 2007, more than half the United Nations member
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states, including those of the European Community, signed a major agreement
on the rights of people with disabilities. The agreement is called the Convention
on the Rights of Persons with Disabilities. It outlaws discrimination against
people with disabilities in all areas of life, including employment, education,
health services, transportation, and access to justice. The next step for the
countries that signed the agreement is to make it part of their national laws.
Jamaica was the first country to do so.
The Way Ahead
Too often, people without disabilities see those who have them only in terms of
their limitations, not in terms of their abilities. Just as medicine helps people with
disabilities live longer and better lives, society needs to help them be full
participants in their communities. This means hiring more people with disabilities.
It also means providing them with more accessible housing.
Governments can contribute by supporting medical research that will help today's
people with disabilities live better lives and that will prevent or lessen disabilities
in the future. They can also support prevention, including safety regulations and
the early detection, diagnosis, and treatment of diseases that lead to disabilities.
Frank Bowe
Hofstra University
Author, Making Inclusion Work
MLA (Modern Language Association) style:
Bowe, Frank. "Disabilities, People with." The New Book of Knowledge®. 2010.
Grolier Online. 15 July 2010 <http://nbk.grolier.com/cgibin/article?assetid=a2007900-h>.
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Mental Illness
[Lexile: 1010L]
An illness is an unhealthy condition that interferes with normal body activities.
Illnesses can be caused by damage to some part of the body or by an
abnormally functioning bodily organ. According to the Surgeon General of the
United States, mental illnesses are "disorders of the brain that disrupt a person's
thinking, feeling, moods, and ability to relate to others."
Just as with other medical illnesses, mental illnesses have special names
(diagnoses) and cause particular symptoms for the people who have them.
These illnesses need to be treated by a psychiatrist, psychologist, social worker,
psychiatric nurse, or other mental health expert. Not all mental illnesses are
curable. But the symptoms will get better with proper treatment. In this way,
mental illnesses are similar to physical illnesses.
An example of a physical illness is diabetes. It is caused when the pancreas
cannot produce enough insulin. This prevents the body from using sugar from the
blood for energy. In some people, the pancreas does not make enough insulin
from early in life. In other people, diabetes is caused by injuries to the pancreas
or excess body weight. Just as problems with the pancreas can cause diabetes,
problems in the brain can also cause illnesses. These problems can be caused
by many different factors, including genetics and the environment.
Types of Mental Illness
In the United States, the different mental illnesses are classified in a book written
by the American Psychiatric Association. The book is titled Diagnostic and
Statistical Manual of Mental Disorders, Fourth Edition, or DSM-IV. The DSM-IV
lists over 400 separate disorders. The most common diagnoses are discussed in
this article.
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Mood Disorders
Most people experience a wide range of different feelings and emotions every
day. Typical feelings include joy, excitement, fear, sadness, anger, jealousy,
pride, and shame. The term "mood" refers to a feeling that lasts for hours, days,
weeks, or longer. Sometimes a particular mood is strong and long lasting. It even
interferes with normal activities. This situation is referred to as a mood disorder.
One kind of mood disorder is depression. This is extreme sadness that causes
loss of pleasure in almost all activities. Children with depression may feel more
irritability than sadness. Major depressive disorder is diagnosed when
depression lasts for two weeks or more and is accompanied by other symptoms.
These are sleep problems (either too much or too little), weight change,
hopelessness, and trouble concentrating. A less severe but more lasting form of
depression is dysthymic disorder.
Depression is one of the most common psychiatric disorders. Approximately 20%
of women will have a major depressive episode during their lives. This is almost
twice the number seen in men.
People with bipolar disorder (also called manic depression) have repeated
episodes of depression that alternate with periods of mania. Or, depression and
mania can be separated by periods of normal mood. Mania is a mood that is
excessively happy or irritable combined with symptoms such as decreased need
for sleep, excessive talking, and racing thoughts. People with mania may have
thoughts that are grandiose. For example, they may believe they have special
powers. Bipolar disorder is less frequent than major depressive disorder. It
occurs equally in men and women.
Depression and bipolar disorder most commonly begin in adulthood. But children
and adolescents can also have these illnesses. Mood disorders of all types tend
to run in families. This is particularly true for mood problems in children. Mood
disorders that start in childhood tend to be more serious and to continue longer.
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All types of mood disorders can be severe and chronic illnesses. They can
usually be well controlled with medicine and other therapy. If left untreated,
however, they sometimes result in suicide.
Anxiety Disorders
Everyone feels fear and anxiety sometimes. A normal fear is associated with a
specific danger in the immediate future. For example, you might be afraid of
being struck by lightning if you are standing outside during a thunderstorm.
Anxiety refers to a more general feeling of worry about the future. It can happen
even when there is no immediate danger. Some anxiety can be good. It
motivates people to work or study in order to keep a job or do well in school. But
too much anxiety can interfere with normal activities. It can undermine a person's
ability to concentrate, make decisions, or even go outside.
A panic attack is a sudden feeling of intense anxiety. It usually includes a fear of
dying or going crazy. The anxiety is combined with physical symptoms such as
sweating, increased heart rate, shortness of breath, dizziness, numbness, or
choking. Some people who have had panic attacks begin to constantly fear
having them again. This is called panic disorder.
People with panic disorder may begin to avoid places or situations where they
would feel trapped if they had a panic attack. This is called agoraphobia. In
some cases, agoraphobia prevents people from traveling or leaving home.
Individuals with social phobia have intense and unreasonable fears of certain
social situations. For example, they may fear they will suffer overwhelming
embarrassment if they have to speak or perform in public.
People with obsessive-compulsive disorder (OCD) have unwanted thoughts,
or obsessions, about a particular danger. For example, they may become
obsessed with being contaminated by germs if they touch a doorknob. These
obsessions cause them to feel intense anxiety and distress. To reduce the
stress, they repeatedly perform a certain act (compulsion) that is related to the
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obsession. For example, they might wash their hands again and again to remove
the germs. Some people with OCD spend many hours each day doing
compulsive acts. They are unable to stop the behavior, even though they realize
their fears are exaggerated.
Post-traumatic stress disorder (PTSD) is seen only after someone has
experienced a very frightening or life-threatening situation. Potential causes of
PTSD include a serious accident, an earthquake, or physical or sexual abuse.
People who experience such an event may relive it through intense memories
and nightmares. They may also have flashbacks (feeling as though the event is
happening again) when they encounter reminders of the situation. People with
PTSD have symptoms of numbing. This is an absence of normal feelings. They
also experience hyperarousal. This is the presence of abnormally intense
feelings such as anger and fear.
Generalized anxiety disorder is a continued state of worry accompanied by
physical symptoms. The worry focuses on upcoming events such as those
related to work or school. Physical symptoms include restlessness, fatigue,
muscle tension, and sleep problems. Anxiety disorders are very common in
children, adolescents, and adults. They are frequently seen along with mood
disorders and other psychiatric problems.
Problems Primarily Affecting Memory
The two types of illnesses that affect memory are delirium and dementia.
Delirium is a condition in which people lose awareness of who they are, where
they are, or what day it is. People who are delirious may be confused and have
trouble communicating. They may also hallucinate. This means they see and
hear things that are not really there. Delirium comes on quickly. It is usually
caused by some physical effect on the brain from a medical condition, poison, or
drug.
Dementia is a gradual loss of memory and judgment. People with dementia lose
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the ability to make decisions and perform routine activities. They lose the ability
to recognize familiar objects, places, and people. Dementia is caused by physical
damage or deterioration of the brain because of injury, illness, or inherited
genetic problems. One type of dementia, Alzheimer's disease, affects
approximately 2 to 4 percent of people over age 65.
Schizophrenia and Other Psychotic Disorders
Psychosis is a term that usually refers to a group of symptoms including
hallucinations, delusions, and disorganized thoughts and speech. These
symptoms can be seen with certain medical conditions. And they can be seen in
people who are intoxicated with certain substances.
The most serious illness with psychotic symptoms is schizophrenia. People with
schizophrenia may have hallucinations. They may also believe falsely that people
are following them or trying to hurt them. These false beliefs are called
delusions. Hallucinations and delusions can cause a great deal of distress and
fear. People with schizophrenia may also have disorganized thoughts and
speech. This makes it difficult for them to study, work, and interact normally with
others.
Schizophrenia occurs in people throughout the world. It usually starts when
individuals are in their 20's. And it tends to run in families. People with
schizophrenia may need lifelong care. But with new treatments and medications,
many people have been able to live independent, productive lives.
Problems with Alcohol and Other Drugs
Serious risks accompany the repeated use of alcohol or other drugs such as
cocaine, heroin, and opiate painkillers. A person who repeatedly uses these
substances may suffer serious consequences in his or her life. The
consequences may include missing school or work, having conflicts at home, or
participating in dangerous behavior, such as driving while intoxicated. If someone
continues to use a substance despite having these types of problems repeatedly,
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the condition is called substance abuse.
Use of alcohol, nicotine, and other drugs can also result in addiction. This means
a person develops physical symptoms if he or she stops using the drug
(withdrawal). It also means a person has to use increasing amounts of the drug
to get the same effect (tolerance). People taking addictive substances may be
unable to stop their drug use even when they know that it is causing them harm.
Eating Disorders
Two major mental illnesses involve abnormal eating behaviors. People with
anorexia nervosa are intensely afraid of gaining weight. They believe
themselves to be fat even when they are thin or underweight. To avoid gaining
weight, people with anorexia nervosa starve themselves and may exercise
excessively. Anorexia can cause lifelong problems of weak bones and hormone
imbalance. It can be fatal if a person's weight falls too low.
The second major type of eating disorder is bulimia nervosa. People with
bulimia feel uncontrollable urges to eat excessively large amounts of food (this is
called bingeing). The binges are followed by attempts to remove the food from
the body by vomiting, using laxatives, or exercising. Some people have a
combination of anorexia and bulimia.
Anorexia nervosa and bulimia nervosa are seen mostly in young women,
typically starting in adolescence. But eating disorders can also affect men. In
some people the symptoms gradually lessen with age. But many people continue
to have problems with eating behavior as adults.
Disorders of Infants, Children, and Adolescents
Some mental illnesses typically start early in life. But they may not be diagnosed
until later or may continue into adulthood. The most frequently occurring of these
disorders include mental retardation, learning and communication problems,
developmental disorders, and attention and disruptive behavior disorders.
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Mental retardation affects approximately 1 percent of the population. It is
characterized by a general, below-average ability to learn (low IQ) and trouble
participating in daily activities. The severity of mental retardation can range from
mild to profound, the most serious type. Most cases are mild. Few are profound.
People who have mild mental retardation can often live and work independently.
Those with profound mental retardation usually need close supervision
throughout life. For more information about mental retardation, see the article
Retardation, Mental.
Individuals with learning and communication disorders have normal
intelligence. But they have difficulty in a particular learning area, such as reading,
mathematics, or writing. Others may have trouble expressing themselves or
understanding language.
Children with pervasive developmental disorders (PDD) have severe problems
in several areas of development. These problems cause difficulty relating to
others. Many children with PDD also have trouble with language and are unable
to communicate normally. Often they show unusual interests or body
movements. Two of the more frequently seen types of PDD are autistic
disorder and Asperger's disorder. For more information about autistic disorder
and Asperger's disorder, see the article Autism.
Attention-deficit/hyperactivity disorder (ADHD) is seen in approximately 3 to
5 percent of school-age children. It occurs mostly in boys. The two major types of
symptoms are inattention and hyperactivity or impulsiveness. Children with
ADHD may lose things, be easily distracted, and have trouble paying attention.
They may also seem to be constantly talking and unable to sit still. All of these
behaviors are normal in children to some degree. ADHD is diagnosed only when
the behaviors are persistent and interfere with normal daily activities at school
and at home. See the article ADHD to learn more.
Personality Disorders
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The term "personality" refers to the typical ways that someone thinks, feels, acts,
and reacts to situations in his or her life. For example, some people may be shy
in new situations, prefer a regular routine, plan ahead, make decisions slowly,
and become worried easily. Other people enjoy meeting others, get bored with
routine, do not plan very far ahead, make decisions quickly, and seldom become
worried or anxious. Both of these personality types are normal, as are many
other possible patterns.
People with personality disorders are those who have developed patterns of
thinking, feeling, and behaving that are much different from those usually seen.
For example, people with paranoid personality disorder are highly suspicious
of other people's intentions. Schizoid personality disorder is characterized by a
strong lack of interest in having relationships with other people. Those with
histrionic personality disorder are highly emotional and seek excessive
attention from others. Individuals with antisocial personality disorder disregard
other people's rights. And people with obsessive-compulsive personality
disorder are excessively preoccupied with things being perfect and in order.
People with personality disorders are unable to change their behavior. It persists
even if it causes problems with personal relationships or an inability to cope with
daily activities.
Personality is formed over a long period of time during childhood and
adolescence. As a result, personality disorders do not appear until late
adolescence or young adulthood. Without treatment, symptoms tend to last for
many years. But some will gradually get better as a person grows older.
Causes of Mental Illness
The exact causes of mental illness are still being discovered. But it is clear that
many result from a combination of biological, psychological, and social problems.
Some types of mental illness, such as depression, are at least partly hereditary.
People inherit genes that make them more likely than other people to develop the
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illness. However, it develops only if certain things happen to them during their
lives. This is known as genetic vulnerability. Mental illnesses that seem to have a
high level of genetic vulnerability include ADHD, mood disorders, schizophrenia,
and some anxiety disorders.
Some mental illnesses show less evidence of being controlled by heredity. They
seem to be the result of life experiences. For example, post-traumatic stress
disorder occurs only if someone has been through a life-threatening event or
traumatic situation. Other mental illnesses, such as substance-abuse disorders,
seem to be caused in almost equal parts by genetics and experience, including
cultural values.
Treatment of Mental Illness
Just as with physical illnesses, the best treatment for a mental illness is different
for different people. The same diagnosis may lead to different treatments.
Treatments may vary if there is more than one diagnosis. And there may be
psychological and social factors that are making the illness worse. Many mental
illnesses are caused by a combination of brain biology and experiences. As a
result, the best treatments often combine biological and non-biological therapies.
The most important biological treatments are medications and electroconvulsive
therapy (ECT). For most mental illnesses, drugs that deliver cures do not yet
exist. But many new drugs help relieve specific symptoms such as depression,
anxiety, obsessions, inattention, and sleep problems. Specialized studies have
begun to show how these medicines affect the parts of the brain that are working
abnormally in different illnesses.
ECT is a treatment during which the patient is put under anesthesia and given a
medicine to prevent muscle contractions. A pulse of electricity is then given to the
brain through electrodes placed on either one or both sides of the head. The way
ECT works is not yet known. However, it has been used to treat severe cases of
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depression and mania that do not respond to other treatments.
Non-biological treatments are often grouped under the term psychotherapy. A
patient undergoing psychotherapy usually has a series of meetings with a mental
health professional. The different types of psychotherapy emphasize different
approaches for dealing with mental illness. Cognitive-behavioral therapy uses
training methods that help people have more self-control over their symptoms.
Family therapy can help change the way people behave toward each other at
home. This can lower stress, improve support, or change habits that may
contribute to symptoms. Individual psychotherapy helps people understand
how experiences in the past affect their behavior in the present. Group therapy
involves several people with the same type of problem working together with a
therapist. It is often helpful in teaching people new ways to cope with their illness.
People can learn from each other when they share their experiences with others
dealing with the same problems.
An exciting discovery has been that certain methods of psychotherapy cause
physical changes in the brain similar to those seen with drug treatment. For
example, cognitive-behavioral therapy and medicine each increase blood flow to
the part of the brain affected in obsessive-compulsive disorder.
Mental Health Professions
In the United States, there are four main professions devoted to treating mental
illness. Psychiatrists are doctors who specialize in evaluating, diagnosing, and
treating people with psychiatric disorders. They can prescribe medication and
use all of the other treatments that help people with mental illness. There are
also sub-specialists in psychiatry. Some concentrate on certain age groups, such
as children. Others concentrate on certain types of problems, such as substance
abuse.
Psychologists are behavioral scientists who study both normal and abnormal
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functioning. They also treat patients with mental and emotional problems using
non-biological treatments. Social workers are professionals devoted to helping
people function the best they can in their environment. This can mean providing
services or therapy directly to people. Or it can mean working to improve social
conditions. Nurses are trained both to provide direct medical care and to help
patients and families learn to provide self-care. Nurses with advanced training in
psychiatric nursing often work with mentally ill patients either in the hospital or in
the community. Some are able to prescribe medication.
The best care for patients usually involves having an assessment by a
psychiatrist, psychologist, social worker, or psychiatric nurse who will either
provide treatment or refer the patient to another specialist. For patients with
complicated, long-lasting, and serious mental illnesses, a group of mental health
professionals (a treatment team) may be necessary.
Where to Get Help
People who need mental health treatment will often go first to their regular
physician. Many physicians can help with uncomplicated problems. But they will
usually need to refer someone to a specialist for a problem that is complicated or
severe. Similarly, most schools have counselors available to meet with students
to help with less serious problems. If more help is needed, counselors can refer
students and their parents to a mental health specialist in the community. Most
communities have public clinics or mental health centers where people can go
directly if they are in need of help. Some communities have hotlines. These are
telephone numbers available 24 hours a day. They provide volunteers or staff
who can help with an emergency or suggest how to find professional help.
Attitudes Toward Mental Illness
Until the 1600's, most cultures did not distinguish mental illness from physical
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illness. During the 1600's, French philosopher René Descartes developed the
idea that the mind and the body were separate. With time, particularly in
European cultures, brain illnesses whose symptoms were mostly problems with
feelings, thinking, and behavior were considered problems of the mind and not
the body. As a result, people began to think differently about mental as opposed
to physical disease.
This separation of illness into two categories had serious implications. One was
that diseases of the mind (mental illness) came to be seen as caused by some
personal failure or weakness. Many caring physicians and religious leaders did
their best to help the mentally ill. But people with mental diseases were often
looked at as inferior, or bad, by society. These negative attitudes have only
slowly begun to change.
In 2005, research supported by the National Institute of Mental Health found that
nearly half of all adults suffer mental illness during their lifetimes. But only about
one-third receive effective treatment.
Scientists have started to discover the brain abnormalities that cause the
symptoms of mental disorders. These discoveries have led to new treatments.
They also challenge ideas that have been used to stigmatize the mentally ill.
Future progress will depend upon more new discoveries about the brain. It will
also depend upon a change in the attitudes of society. These attitudes have
prevented people with mental illness from receiving the care they need.
Robert Racusin, M.D.
Associate Professor of Psychiatry Dartmouth Medical
School
MLA (Modern Language Association) style:
Racusin, Robert. "Mental Illness." The New Book of Knowledge®. 2010. Grolier
Online. 15 July 2010 <http://nbk.grolier.com/cgi-bin/article?assetid=a2018950-h>.
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