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=                                Pain                                =
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                             Introduction                             
======================================================================
Pain is a distressing feeling often caused by intense or damaging
stimuli. The International Association for the Study of Pain's widely
used definition defines pain as "An unpleasant sensory and emotional
experience associated with, or resembling that associated with, actual
or potential tissue damage". In medical diagnosis, pain is regarded as
a symptom of an underlying condition.

Pain motivates the individual to withdraw from damaging situations, to
protect a damaged body part while it heals, and to avoid similar
experiences in the future. Most pain resolves once the noxious
stimulus is removed and the body has healed, but it may persist
despite removal of the stimulus and apparent healing of the body.
Sometimes pain arises in the absence of any detectable stimulus,
damage or disease.

Pain is the most common reason for physician consultation in most
developed countries. It is a major symptom in many medical conditions,
and can interfere with a person's quality of life and general
functioning. Simple pain medications are useful in 20% to 70% of
cases. Psychological factors such as social support, hypnotic
suggestion, cognitive behavioral therapy, excitement, or distraction
can affect pain's intensity or unpleasantness. In some debates
regarding physician-assisted suicide or euthanasia, pain has been used
as an argument to permit people who are terminally ill to end their
lives.


 Duration 
==========
Pain is usually transitory, lasting only until the noxious stimulus is
removed or the underlying damage or pathology has healed, but some
painful conditions, such as rheumatoid arthritis, peripheral
neuropathy, cancer and idiopathic pain, may persist for years. Pain
that lasts a long time is called 'chronic' or persistent, and pain
that resolves quickly is called 'acute'. Traditionally, the
distinction between 'acute' and 'chronic' pain has relied upon an
arbitrary interval of time between onset and resolution; the two most
commonly used markers being 3 months and 6 months since the onset of
pain, though some theorists and researchers have placed the transition
from acute to chronic pain at 12 months. Others apply 'acute' to pain
that lasts less than 30 days, 'chronic' to pain of more than six
months' duration, and 'subacute' to pain that lasts from one to six
months.  A popular alternative definition of 'chronic pain', involving
no arbitrarily fixed durations, is "pain that extends beyond the
expected period of healing". Chronic pain may be classified as cancer
pain or else as benign.


 Allodynia 
===========
Allodynia is pain experienced in response to a normally painless
stimulus.  It has no biological function and is classified by stimuli
into dynamic mechanical, punctate and static. In osteoarthritis, NGF
has been identified as being involved in allodynia. The extent and
intensity of sensation can be assessed through locating trigger points
and the region of sensation, as well as utilising phantom maps.


 Phantom 
=========
Phantom pain is pain felt in a part of the body that has been
amputated, or from which the brain no longer receives signals. It is a
type of neuropathic pain.

The prevalence of phantom pain in upper limb amputees is nearly 82%,
and in lower limb amputees is 54%. One study found that eight days
after amputation, 72% of patients had phantom limb pain, and six
months later, 67% reported it. Some amputees experience continuous
pain that varies in intensity or quality; others experience several
bouts of pain per day, or it may reoccur less often. It is often
described as shooting, crushing, burning or cramping. If the pain is
continuous for a long period, parts of the intact body may become
sensitized, so that touching them evokes pain in the phantom limb.
Phantom limb pain may accompany urination or defecation.

Local anesthetic injections into the nerves or sensitive areas of the
stump may relieve pain for days, weeks, or sometimes permanently,
despite the drug wearing off in a matter of hours; and small
injections of hypertonic saline into the soft tissue between vertebrae
produces local pain that radiates into the phantom limb for ten
minutes or so and may be followed by hours, weeks or even longer of
partial or total relief from phantom pain. Vigorous vibration or
electrical stimulation of the stump, or current from electrodes
surgically implanted onto the spinal cord, all produce relief in some
patients.

Mirror box therapy produces the illusion of movement and touch in a
phantom limb which in turn may cause a reduction in pain.

Paraplegia, the loss of sensation and voluntary motor control after
serious spinal cord damage, may be accompanied by girdle pain at the
level of the spinal cord damage, visceral pain evoked by a filling
bladder or bowel, or, in five to ten per cent of paraplegics, phantom
body pain in areas of complete sensory loss. This phantom body pain is
initially described as burning or tingling but may evolve into severe
crushing or pinching pain, or the sensation of fire running down the
legs or of a knife twisting in the flesh. Onset may be immediate or
may not occur until years after the disabling injury. Surgical
treatment rarely provides lasting relief.


 Breakthrough{{anchor|Breakthrough_pain}} 
==========================================
Breakthrough pain is transitory pain that comes on suddenly and is not
alleviated by the patient's regular pain management. It is common in
cancer patients who often have background pain that is generally
well-controlled by medications, but who also sometimes experience
bouts of severe pain that from time to time "breaks through" the
medication. The characteristics of breakthrough cancer pain vary from
person to person and according to the cause. Management of
breakthrough pain can entail intensive use of opioids, including
fentanyl.


 Asymbolia and insensitivity 
=============================
The ability to experience pain is essential for protection from
injury, and recognition of the presence of injury. Episodic analgesia
may occur under special circumstances, such as in the excitement of
sport or war: a soldier on the battlefield may feel no pain for many
hours from a traumatic amputation or other severe injury.

Although unpleasantness is an essential part of the IASP definition of
pain, it is possible to induce a state described as intense pain
devoid of unpleasantness in some patients, with morphine injection or
psychosurgery. Such patients report that they have pain but are not
bothered by it; they recognize the sensation of pain but suffer
little, or not at all. Indifference to pain can also rarely be present
from birth; these people have normal nerves on medical investigations,
and find pain unpleasant, but do not avoid repetition of the pain
stimulus.

Insensitivity to pain may also result from abnormalities in the
nervous system. This is usually the result of acquired damage to the
nerves, such as spinal cord injury, diabetes mellitus (diabetic
neuropathy), or leprosy in countries where that disease is prevalent.
These individuals are at risk of tissue damage and infection due to
undiscovered injuries. People with diabetes-related nerve damage, for
instance, sustain poorly-healing foot ulcers as a result of decreased
sensation.

A much smaller number of people are insensitive to pain due to an
inborn abnormality of the nervous system, known as "congenital
insensitivity to pain". Children with this condition incur
carelessly-repeated damage to their tongues, eyes, joints, skin, and
muscles. Some die before adulthood, and others have a reduced life
expectancy. Most people with congenital insensitivity to pain have one
of five hereditary sensory and autonomic neuropathies (which includes
familial dysautonomia and congenital insensitivity to pain with
anhidrosis). These conditions feature decreased sensitivity to pain
together with other neurological abnormalities, particularly of the
autonomic nervous system. A very rare syndrome with isolated
congenital insensitivity to pain has been linked with mutations in the
'SCN9A' gene, which codes for a sodium channel (Nav1.7) necessary in
conducting pain nerve stimuli.


                          Functional effects                          
======================================================================
Experimental subjects challenged by acute pain and patients in chronic
pain experience impairments in attention control, working memory,
mental flexibility, problem solving, and information processing speed.
Acute and chronic pain are also associated with increased depression,
anxiety, fear, and anger.


 On subsequent negative emotion 
================================
Although pain is considered to be aversive and unpleasant and is
therefore usually avoided, a meta-analysis which summarized and
evaluated numerous studies from various psychological disciplines,
found a reduction in negative affect. Across studies, participants
that were subjected to acute physical pain in the laboratory
subsequently reported feeling better than those in non-painful control
conditions, a finding which was also reflected in physiological
parameters. A potential mechanism to explain this effect is provided
by the opponent-process theory.


 Historical<!--linked from 'Patrick David Wall'--> 
===================================================
Before the relatively recent discovery of neurons and their role in
pain, various different body functions were proposed to account for
pain. There were several competing early theories of pain among the
ancient Greeks: Hippocrates believed that it was due to an imbalance
in vital fluids. In the 11th century, Avicenna theorized that there
were a number of feeling senses including touch, pain and titillation.

In 1644, René Descartes theorized that pain was a disturbance that
passed down along nerve fibers until the disturbance reached the
brain. Descartes's work, along with Avicenna's, prefigured the
19th-century development of specificity theory. Specificity theory saw
pain as "a specific sensation, with its own sensory apparatus
independent of touch and other senses". Another theory that came to
prominence in the 18th and 19th centuries was intensive theory, which
conceived of pain not as a unique sensory modality, but an emotional
state produced by stronger than normal stimuli such as intense light,
pressure or temperature. By the mid-1890s, specificity was backed
mostly by physiologists and physicians, and the intensive theory was
mostly backed by psychologists. However, after a series of clinical
observations by Henry Head and experiments by Max von Frey, the
psychologists migrated to specificity almost en masse, and by
century's end, most textbooks on physiology and psychology were
presenting pain specificity as fact.


 Modern 
========
Wilhelm Erb's (1874) "intensive" theory, that a pain signal can be
generated by intense enough stimulation of 'any' sensory receptor, has
been soundly disproved. Some sensory fibers do not differentiate
between noxious and non-noxious stimuli, while others, nociceptors,
respond only to noxious, high intensity stimuli. At the peripheral end
of the nociceptor, noxious stimuli generate currents that, above a
given threshold, send signals along the nerve fiber to the spinal
cord. The "specificity" (whether it responds to thermal, chemical or
mechanical features of its environment) of a nociceptor is determined
by which ion channels it expresses at its peripheral end. Dozens of
different types of nociceptor ion channels have so far been
identified, and their exact functions are still being determined.

The pain signal travels from the periphery to the spinal cord along an
A-delta or C fiber. Because the A-delta fiber is thicker than the C
fiber, and is thinly sheathed in an electrically insulating material
(myelin), it carries its signal faster (5-30 m/s) than the
unmyelinated C fiber (0.5-2 m/s). Pain evoked by the A-delta fibers is
described as sharp and is felt first. This is followed by a duller
pain, often described as burning, carried by the C fibers. These
"first order" neurons enter the spinal cord via Lissauer's tract.

These A-delta and C fibers connect with "second order" nerve fibers in
the central gelatinous substance of the spinal cord (laminae II and
III of the dorsal horns). The second order fibers then cross the cord
via the anterior white commissure and ascend in the spinothalamic
tract. Before reaching the brain, the spinothalamic tract splits into
the lateral, neospinothalamic tract and the medial, paleospinothalamic
tract.

Second order, spinal cord fibers dedicated to carrying A-delta fiber
pain signals, and others that carry both A-delta and C fiber pain
signals to the thalamus have been identified. Other spinal cord
fibers, known as wide dynamic range neurons, respond to A-delta and C
fibers, but also to the large A-beta fibers that carry touch, pressure
and vibration signals. Pain-related activity in the thalamus spreads
to the insular cortex (thought to embody, among other things, the
feeling that distinguishes pain from other homeostatic emotions such
as itch and nausea) and anterior cingulate cortex (thought to embody,
among other things, the affective/motivational element, the
unpleasantness of pain). Pain that is distinctly located also
activates primary and secondary somatosensory cortex.

In 1955, DC Sinclair and G Weddell developed peripheral pattern
theory, based on a 1934 suggestion by John Paul Nafe. They proposed
that all skin fiber endings (with the exception of those innervating
hair cells) are identical, and that pain is produced by intense
stimulation of these fibers. Another 20th-century theory was gate
control theory, introduced by Ronald Melzack and Patrick Wall in the
1965 'Science' article "Pain Mechanisms: A New Theory". The authors
proposed that both thin (pain) and large diameter (touch, pressure,
vibration) nerve fibers carry information from the site of injury to
two destinations in the dorsal horn of the spinal cord, and that the
more large fiber activity relative to thin fiber activity at the
inhibitory cell, the less pain is felt.


 Three dimensions of pain 
==========================
In 1968 Ronald Melzack and Kenneth Casey described chronic pain in
terms of its three dimensions:


and duration of the pain),

unpleasantness), and

values, distraction and hypnotic suggestion).

They theorized that pain intensity (the sensory discriminative
dimension) and unpleasantness (the affective-motivational dimension)
are not simply determined by the magnitude of the painful stimulus,
but "higher" cognitive activities can influence perceived intensity
and unpleasantness. Cognitive activities "may affect both sensory and
affective experience or they may modify primarily the
affective-motivational dimension. Thus, excitement in games or war
appears to block both dimensions of pain, while suggestion and
placebos may modulate the affective-motivational dimension and leave
the sensory-discriminative dimension relatively undisturbed." (p. 432)
The paper ends with a call to action: "Pain can be treated not only by
trying to cut down the sensory input by anesthetic block, surgical
intervention and the like, but also by influencing the
motivational-affective and cognitive factors as well." (p. 435)


                   Evolutionary and behavioral role                   
======================================================================
Pain is part of the body's defense system, producing a reflexive
retraction from the painful stimulus, and tendencies to protect the
affected body part while it heals, and avoid that harmful situation in
the future. It is an important part of animal life, vital to healthy
survival. People with congenital insensitivity to pain have reduced
life expectancy.

In 'The Greatest Show on Earth: The Evidence for Evolution', biologist
Richard Dawkins addresses the question of why pain should have the
quality of being painful. He describes the alternative as a mental
raising of a "red flag". To argue why that red flag might be
insufficient, Dawkins argues that drives must compete with one other
within living beings. The most "fit" creature would be the one whose
pains are well balanced. Those pains which mean certain death when
ignored will become the most powerfully felt. The relative intensities
of pain, then, may resemble the relative importance of that risk to
our ancestors. This resemblance will not be perfect, however, because
natural selection can be a poor designer. This may have maladaptive
results such as supernormal stimuli.

Pain, however, does not only wave a "red flag" within living beings
but may also act as a warning sign and a call for help to other living
beings. Especially in humans who readily helped each other in case of
sickness or injury throughout their evolutionary history, pain might
be shaped by natural selection to be a credible and convincing signal
of need for relief, help, and care.

Idiopathic pain (pain that persists after the trauma or pathology has
healed, or that arises without any apparent cause) may be an exception
to the idea that pain is helpful to survival, although some
psychodynamic psychologists argue that such pain is psychogenic,
enlisted as a protective distraction to keep dangerous emotions
unconscious.


                              Thresholds                              
======================================================================
In pain science, thresholds are measured by gradually increasing the
intensity of a stimulus in a procedure called quantitative sensory
testing which involves such stimuli as electric current, thermal (heat
or cold), mechanical (pressure, touch, vibration), ischemic, or
chemical stimuli applied to the subject to evoke a response. The "pain
perception threshold" is the point at which the subject begins to feel
pain, and the "pain threshold intensity" is the stimulus intensity at
which the stimulus begins to hurt. The "pain tolerance threshold" is
reached when the subject acts to stop the pain.


                              Assessment                              
======================================================================
A person's self-report is the most reliable measure of pain.  Some
health care professionals may underestimate pain severity. A
definition of pain widely employed in nursing, emphasizing its
subjective nature and the importance of believing patient reports, was
introduced by Margo McCaffery in 1968: "Pain is whatever the
experiencing person says it is, existing whenever he says it
does".More recently, McCaffery defined pain as "whatever the
experiencing person says it is, existing whenever the experiencing
person says it does."  To assess intensity, the patient may be asked
to locate their pain on a scale of 0 to 10, with 0 being no pain at
all, and 10 the worst pain they have ever felt. Quality can be
established by having the patient complete the McGill Pain
Questionnaire indicating which words best describe their pain.


 Visual analogue scale 
=======================
The visual analogue scale is a common, reproducible tool in the
assessment of pain and pain relief. The scale is a continuous line
anchored by verbal descriptors, one for each extreme of pain where a
higher score indicates greater pain intensity. It is usually 10 cm in
length with no intermediate descriptors as to avoid marking of scores
around a preferred numeric value. When applied as a pain descriptor,
these anchors are often 'no pain' and 'worst imaginable pain".
Cut-offs for pain classification have been recommended as no pain
(0-4mm), mild pain (5-44mm), moderate pain (45-74mm) and severe pain
(75-100mm).


 Multidimensional pain inventory 
=================================
The Multidimensional Pain Inventory (MPI) is a questionnaire designed
to assess the psychosocial state of a person with chronic pain.
Combining the MPI characterization of the person with their IASP
five-category pain profile is recommended for deriving the most useful
case description.


 Assessment in non-verbal people 
=================================
Non-verbal people cannot use words to tell others that they are
experiencing pain.  However, they may be able to communicate through
other means, such as blinking, pointing, or nodding.

With a non-communicative person, observation becomes critical, and
specific behaviors can be monitored as pain indicators. Behaviors such
as facial grimacing and guarding (trying to protect part of the body
from being bumped or touched) indicate pain, as well as an increase or
decrease in vocalizations, changes in routine behavior patterns and
mental status changes. Patients experiencing pain may exhibit
withdrawn social behavior and possibly experience a decreased appetite
and decreased nutritional intake. A change in condition that deviates
from baseline, such as moaning with movement or when manipulating a
body part, and limited range of motion are also potential pain
indicators. In patients who possess language but are incapable of
expressing themselves effectively, such as those with dementia, an
increase in confusion or display of aggressive behaviors or agitation
may signal that discomfort exists, and further assessment is
necessary.  Changes in behavior may be noticed by caregivers who are
familiar with the person's normal behavior.

Infants do feel pain, but lack the language needed to report it, and
so communicate distress by crying. A non-verbal pain assessment should
be conducted involving the parents, who will notice changes in the
infant which may not be obvious to the health care provider. Pre-term
babies are more sensitive to painful stimuli than those carried to
full term.

Another approach, when pain is suspected, is to give the person
treatment for pain, and then watch to see whether the suspected
indicators of pain subside.


 Other reporting barriers 
==========================
The way in which one experiences and responds to pain is related to
sociocultural characteristics, such as gender, ethnicity, and age. An
aging adult may not respond to pain in the same way that a younger
person might. Their ability to recognize pain may be blunted by
illness or the use of medication. Depression may also keep older adult
from reporting they are in pain. Decline in self-care may also
indicate the older adult is experiencing pain. They may be reluctant
to report pain because they do not want to be perceived as weak, or
may feel it is impolite or shameful to complain, or they may feel the
pain is a form of deserved punishment.

Cultural barriers may also affect the likelihood of reporting pain.
Sufferers may feel that certain treatments go against their religious
beliefs. They may not report pain because they feel it is a sign that
death is near. Many people fear the stigma of addiction, and avoid
pain treatment so as not to be prescribed potentially addicting drugs.
Many Asians do not want to lose respect in society by admitting they
are in pain and need help, believing the pain should be borne in
silence, while other cultures feel they should report pain immediately
to receive immediate relief.

Gender can also be a perceived factor in reporting pain. Gender
differences can be the result of social and cultural expectations,
with women expected to be more emotional and show pain, and men more
stoic. As a result, female pain is often stigmatized, leading to less
urgent treatment of women based on social expectations of their
ability to accurately report it.  This leads to extended emergency
room wait times for women and frequent dismissal of their ability to
accurately report pain.


 Diagnostic aid 
================
Pain is a symptom of many medical conditions. Knowing the time of
onset, location, intensity, pattern of occurrence (continuous,
intermittent, etc.), exacerbating and relieving factors, and quality
(burning, sharp, etc.) of the pain will help the examining physician
to accurately diagnose the problem. For example, chest pain described
as extreme heaviness may indicate myocardial infarction, while chest
pain described as tearing may indicate aortic dissection.


 Physiological measurement 
===========================
Functional magnetic resonance imaging brain scanning has been used to
measure pain, and correlates well with self-reported pain.


 Nociceptive 
=============
Nociceptive pain is caused by stimulation of sensory nerve fibers that
respond to stimuli approaching or exceeding harmful intensity
(nociceptors), and may be classified according to the mode of noxious
stimulation. The most common categories are "thermal" (e.g. heat or
cold), "mechanical" (e.g. crushing, tearing, shearing, etc.) and
"chemical" (e.g. iodine in a cut or chemicals released during
inflammation). Some nociceptors respond to more than one of these
modalities and are consequently designated polymodal.

Nociceptive pain may also be classed according to the site of origin
and divided into "visceral", "deep somatic" and "superficial somatic"
pain. Visceral structures (e.g., the heart, liver and intestines) are
highly sensitive to stretch, ischemia and inflammation, but relatively
insensitive to other stimuli that normally evoke pain in other
structures, such as burning and cutting. Visceral pain is diffuse,
difficult to locate and often referred to a distant, usually
superficial, structure. It may be accompanied by nausea and vomiting
and may be described as sickening, deep, squeezing, and dull. 'Deep
somatic' pain is initiated by stimulation of nociceptors in ligaments,
tendons, bones, blood vessels, fasciae and muscles, and is dull,
aching, poorly-localized pain. Examples include sprains and broken
bones. 'Superficial somatic' pain is initiated by activation of
nociceptors in the skin or other superficial tissue, and is sharp,
well-defined and clearly located. Examples of injuries that produce
superficial somatic pain include minor wounds and minor (first degree)
burns.


 Neuropathic 
=============
Neuropathic pain is caused by damage or disease affecting any part of
the nervous system involved in bodily feelings (the somatosensory
system). Neuropathic pain may be divided into peripheral, central, or
mixed (peripheral and central) neuropathic pain. Peripheral
neuropathic pain is often described as "burning", "tingling",
"electrical", "stabbing", or "pins and needles". Bumping the "funny
bone" elicits acute peripheral neuropathic pain.


 Nociplastic 
=============
Nociplastic pain is pain characterized by a changed nociception (but
without evidence of real or threatened tissue damage, or without
disease or damage in the somatosensory system).

This applies, for example, to fibromyalgia patients.


 Psychogenic 
=============
Psychogenic pain, also called 'psychalgia' or 'somatoform pain', is
pain caused, increased, or prolonged by mental, emotional, or
behavioral factors. Headache, back pain, and stomach pain are
sometimes diagnosed as psychogenic. Sufferers are often stigmatized,
because both medical professionals and the general public tend to
think that pain from a psychological source is not "real". However,
specialists consider that it is no less actual or hurtful than pain
from any other source.

People with long-term pain frequently display psychological
disturbance, with elevated scores on the Minnesota Multiphasic
Personality Inventory scales of hysteria, depression and
hypochondriasis (the "neurotic triad"). Some investigators have argued
that it is this neuroticism that causes acute pain to turn chronic,
but clinical evidence points the other direction, to chronic pain
causing neuroticism. When long-term pain is relieved by therapeutic
intervention, scores on the neurotic triad and anxiety fall, often to
normal levels. Self-esteem, often low in chronic pain patients, also
shows improvement once pain has resolved.


                              Management                              
======================================================================
Inadequate treatment of pain is widespread throughout surgical wards,
intensive care units, and accident and emergency departments, in
general practice, in the management of all forms of chronic pain
including cancer pain, and in end of life care.  This neglect extends
to all ages, from newborns to medically frail elderly. African and
Hispanic Americans are more likely than others to suffer unnecessarily
while in the care of a physician; and women's pain is more likely to
be undertreated than men's.

The International Association for the Study of Pain advocates that the
relief of pain should be recognized as a human right, that chronic
pain should be considered a disease in its own right, and that pain
medicine should have the full status of a medical specialty. It is a
specialty only in China and Australia at this time. Elsewhere, pain
medicine is a subspecialty under disciplines such as anesthesiology,
physiatry, neurology, palliative medicine and psychiatry. In 2011,
Human Rights Watch alerted that tens of millions of people worldwide
are still denied access to inexpensive medications for severe pain.


 Medication 
============
Acute pain is usually managed with medications such as analgesics and
anesthetics. Caffeine when added to pain medications such as
ibuprofen, may provide some additional benefit. Ketamine can be used
instead of opioids for short term pain. Management of chronic pain,
however, is more difficult, and may require the coordinated efforts of
a pain management team, which typically includes medical
practitioners, clinical pharmacists, clinical psychologists,
physiotherapists, occupational therapists, physician assistants, and
nurse practitioners.




Sugar (sucrose) when taken by mouth reduces pain in newborn babies
undergoing some medical procedures (a lancing of the heel,
venipuncture, and intramuscular injections). Sugar does not remove
pain from circumcision, and it is unknown if sugar reduces pain for
other procedures.
Sugar did not affect pain-related electrical activity in the brains of
newborns one second after the heel lance procedure. Sweet liquid by
mouth moderately reduces the rate and duration of crying caused by
immunization injection in children between one and twelve months of
age.


 Psychological 
===============
Individuals with more social support experience less cancer pain, take
less pain medication, report less labor pain and are less likely to
use epidural anesthesia during childbirth, or suffer from chest pain
after coronary artery bypass surgery.

Suggestion can significantly affect pain intensity. About 35% of
people report marked relief after receiving a saline injection they
believed to be morphine. This placebo effect is more pronounced in
people who are prone to anxiety, and so anxiety reduction may account
for some of the effect, but it does not account for all of it.
Placebos are more effective for intense pain than mild pain; and they
produce progressively weaker effects with repeated administration. It
is possible for many with chronic pain to become so absorbed in an
activity or entertainment that the pain is no longer felt, or is
greatly diminished.

Cognitive behavioral therapy (CBT) has been shown effective for
improving quality of life in those with chronic pain but the reduction
in suffering is modest, and the CBT method was not shown to have any
effect on outcome. Acceptance and commitment therapy (ACT) may also be
effective in the treatment of chronic pain, as may mindfulness-based
pain management (MBPM).

A number of meta-analyses have found clinical hypnosis to be effective
in controlling pain associated with diagnostic and surgical procedures
in both adults and children, as well as pain associated with cancer
and childbirth. A 2007 review of 13 studies found evidence for the
efficacy of hypnosis in the reduction of chronic pain under some
conditions, though the number of patients enrolled in the studies was
low, raising issues related to the statistical power to detect group
differences, and most lacked credible controls for placebo or
expectation. The authors concluded that "although the findings provide
support for the general applicability of hypnosis in the treatment of
chronic pain, considerably more research will be needed to fully
determine the effects of hypnosis for different chronic-pain
conditions."


 Alternative medicine 
======================
An analysis of the 13 highest quality studies of pain treatment with
acupuncture, published in January 2009, concluded there was little
difference in the effect of real, faked and no acupuncture. However,
more recent reviews have found some benefit. Additionally, there is
tentative evidence for a few herbal medicines. There has been some
interest in the relationship between vitamin D and pain, but the
evidence so far from controlled trials for such a relationship, other
than in osteomalacia, is inconclusive.

For chronic (long-term) lower back pain, spinal manipulation produces
tiny, clinically insignificant, short-term improvements in pain and
function, compared sham therapy and other interventions. Spinal
manipulation produces the same outcome as other treatments, such as
general practitioner care, pain-relief drugs, physical therapy, and
exercise, for acute (short-term) lower back pain.


                             Epidemiology                             
======================================================================
Pain is the main reason for visiting an emergency department in more
than 50% of cases, and is present in 30% of family practice visits.
Several epidemiological studies have reported widely varying
prevalence rates for chronic pain, ranging from 12 to 80% of the
population. It becomes more common as people approach death. A study
of 4,703 patients found that 26% had pain in the last two years of
life, increasing to 46% in the last month.

A survey of 6,636 children (0-18 years of age) found that, of the
5,424 respondents, 54% had experienced pain in the preceding three
months. A quarter reported having experienced recurrent or continuous
pain for three months or more, and a third of these reported frequent
and intense pain. The intensity of chronic pain was higher for girls,
and girls' reports of chronic pain increased markedly between ages 12
and 14.


                               History                                
======================================================================
In 1994, responding to the need for a more useful system for
describing chronic pain, the International Association for the Study
of Pain (IASP) classified pain according to specific characteristics:
# region of the body involved (e.g. abdomen, lower limbs),
# system whose dysfunction may be causing the pain (e.g., nervous,
gastrointestinal),
# duration and pattern of occurrence,
# intensity and time since onset, and
# cause
However, this system has been criticized by Clifford J. Woolf and
others as inadequate for guiding research and treatment.
Woolf suggests three classes of pain:
# nociceptive pain,
# inflammatory pain which is associated with tissue damage and the
infiltration of immune cells, and
# pathological pain which is a disease state caused by damage to the
nervous system or by its abnormal function (e.g. fibromyalgia,
peripheral neuropathy, tension type headache, etc.).


                         Society and culture                          
======================================================================
The nature or meaning of physical pain has been diversely understood
by religious or secular traditions from antiquity to modern times.

Physical pain is an important political topic in relation to various
issues, including pain management policy, drug control, animal rights
or animal welfare, torture, and pain compliance. In various contexts,
the deliberate infliction of pain in the form of corporal punishment
is used as retribution for an offence, or for the purpose of
disciplining or reforming a wrongdoer, or to deter attitudes or
behaviour deemed unacceptable. The slow slicing, or death by a
thousand cuts, was a form of execution in China reserved for crimes
viewed as especially severe, such as high treason or patricide. In
some cultures, extreme practices such as mortification of the flesh or
painful rites of passage are highly regarded. For example, the
Sateré-Mawé people of Brazil use intentional bullet ant stings as part
of their initiation rites to become warriors.


                              Non-humans                              
======================================================================
The most reliable method for assessing pain in most humans is by
asking a question: a person may report pain that cannot be detected by
any known physiological measure. However, like infants, animals cannot
answer questions about whether they feel pain; thus the defining
criterion for pain in humans cannot be applied to them. Philosophers
and scientists have responded to this difficulty in a variety of ways.
René Descartes for example argued that animals lack consciousness and
therefore do not experience pain and suffering in the way that humans
do. Bernard Rollin of Colorado State University, the principal author
of two U.S. federal laws regulating pain relief for animals, writes
that researchers remained unsure into the 1980s as to whether animals
experience pain, and that veterinarians trained in the U.S. before
1989 were simply taught to ignore animal pain. In his interactions
with scientists and other veterinarians, he was regularly asked to
"prove" that animals are conscious, and to provide "scientifically
acceptable" grounds for claiming that they feel pain. Carbone writes
that the view that animals feel pain differently is now a minority
view. Academic reviews of the topic are more equivocal, noting that
although the argument that animals have at least simple conscious
thoughts and feelings has strong support, some critics continue to
question how reliably animal mental states can be determined. The
ability of invertebrate species of animals, such as insects, to feel
pain and suffering is also unclear.

The presence of pain in an animal cannot be known for certain, but it
can be inferred through physical and behavioral reactions. Specialists
currently believe that all vertebrates can feel pain, and that certain
invertebrates, like the octopus, may also. As for other animals,
plants, or other entities, their ability to feel physical pain is at
present a question beyond scientific reach, since no mechanism is
known by which they could have such a feeling. In particular, there
are no known nociceptors in groups such as plants, fungi, and most
insects, except for instance in fruit flies.

In vertebrates, endogenous opioids are neuromodulators that moderate
pain by interacting with opioid receptors. Opioids and opioid
receptors occur naturally in crustaceans and, although at present no
certain conclusion can be drawn, their presence indicates that
lobsters may be able to experience pain. Opioids may mediate their
pain in the same way as in vertebrates. Veterinary medicine uses, for
actual or potential animal pain, the same analgesics and anesthetics
as used in humans.


                              Etymology                               
======================================================================
First attested in English in 1297, the word 'peyn' comes from the Old
French 'peine', in turn from Latin 'poena' meaning "punishment,
penalty" (in L.L. also meaning "torment, hardship, suffering") and
that from Greek ποινή ('poine'), generally meaning "price paid,
penalty, punishment".


                               See also                               
======================================================================

stable level of happiness despite major positive or negative events

stress caused from an injury

and physical pain


                            External links                            
======================================================================

Encyclopedia of Philosophy'


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Original Article: http://en.wikipedia.org/wiki/Pain


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