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Dr. Reem Al-Sabah
Faculty of Medicine
What is pain?
Pain is “an unpleasant sensory and emotional
experience associated with actual or potential
tissue damage or described in terms of such
(The International Association for the Study of Pain)
Pain is an almost universal experience, yet difficult to
Clinical Pain: Pain that requires some form of
Pain is the most common reason people seek
Pain appears to have an obvious function.
Why do we have pain?
It provides constant feedback about the body
enabling us to make adjustments to how we sit or
A warning sign that something is wrong resulting in
It triggers help-seeking behavior .
It has psychological consequences and can generate
fear and anxiety.
Types of Pain
Pain has been classified into three stages:
1. Acute. adaptive and meaningful (pain from cuts, burns,
surgery, and other injuries).
2. Chronic. When enough time for normal healing has
elapsed but the pain shows few signs of going away
(6months to years). Often experienced in the absence of
any detectable tissue damage.
3. Prechronic. A critical time when the person either
begins to heal and overcome the pain or lose hope and
develop feelings of helplessness that lead to chronic
The process by which afferent nerve endings translate
noxious stimuli (e.g., a bee sting) into nociceptive
There are three types of primary afferents:
1. A-beta carry information related to touch
2. A-delta information related to pain and temperature
3. C-fibers information related to pain, temperature and itch
Nociceptors: receptors in the skin and organs that sense heat,
mechanical and chemical tissue damage.
Nociception: the process of perceiving pain.
Is the process by which impulses are sent to the dorsal
horn of the spinal cord, and then along the sensory tracts
to the brain.
Pain impulses are transmitted by two fiber systems:
1. fast, sharp and well localized sensation (first pain)
which is conducted by A-delta fibers.
2. duller slower onset and often poorly localized
sensation (second pain) which is conducted by C-
It is the process of either dampening or amplifying the
pain-related neural signals.
Periaqueductal gray (PAG) in the midbrain is
involved in modualting of pain.
descending inhibitory input dampens, or entirely
blocks incoming (ascending) nociceptive signals at the
“gate” of the dorsal horns.
The conscious awareness of the experience of pain.
Perception results from the interaction of
transduction, transmission, modulation, psychological
aspects, and other characteristics of the individual.
Early Pain Theories
Pain is an automatic response to an external factor.
Tissue damage causes the sensation of pain.
The pain sensation has a single cause.
Psychological factors have no causal influence.
Pain was categorized into psychogenic or
Psychogenic pain: considered to be “all in the
patient’s mind” and was a label given to pain
when no organic basis could be found.
Organic pain: regarded as “real pain” and was
the label given to pain when some clear injury
could be seen
Including psychology in theories of pain
Several Observations in the 1920s:
1. Medical treatments for pain (e.g., drugs, surgery)
were generally only useful for treating acute pain,
and ineffective in treating chronic pain.
2. Individual’s with the same degree of tissue
damage, different in their reports of pain and/or
pain expression (e.g. Beecher, 1956).
3. Phantom limb pain (65% to 85% of amputees).
Gate Control Theory
Proposed by Melzack & Wall (1965)
The idea that there is a neural “gate” in the spinal
cord that regulates the experience of pain.
Pain is not the result of a straight-through
Physiological and psychological causes.
Descending central influences from the brain.
The brain sends information related to the
psychological state of the individual to the gate.
Behavioral state (e.g., attention, focus on the
source of pain).
Emotional state (e.g., anxiety, fear, depression).
Previous experience or self-efficacy I dealing with
the pain (e.g., I have experienced this pain before
and know that it will go away).
How does the GCT differ from earlier
models of pain?
Pain as a perception
According to the GCT, pain is a perception and
experience rather than a sensation.
The individual as active, not passive
The individual no longer just responds passively
to painful stimuli, but actively interprets and
appraises this stimuli.
The role of individual variability
Variations in pain perception is understood in
terms of the degree of opening or closing of the
The role of multiple causes
The GCT suggests that many factors are involved
in pain perception, not just a singular physical
Is pain ever organic?
The GCT describes most pain as a
combination of physical and psychological.
Pain and dualism
The GCT suggests an interaction between the
mind and the body.
What opens the gate?
The more the gate is opened, the greater the
perception of pain.
Several factors open the gate:
Physical factors (e.g., injury, activation of the large
Emotional factors (e.g., anxiety, worry, depression)
Behavioral factors (focusing on the pain, boredom)
What closes the gate?
Closing the gate reduces pain perception.
Certain factors close the gate:
Physical factors (e.g., medication, stimulation of
the small fibers)
Emotional factors (e.g., happiness, optimism,
Behavioral factors (focus, concentration,
distraction, or involvement in other activities)
Attention Catastroph behavior
The role of psychosocial
factors in pain perception
Three-process-model of pain
1. Physiological processes (e.g., tissue damage, the
release of endorphins and changes in heart rate)
2. Subjective-affective-cognitive processes
3. Behavioral processes
The role of learning
(e.g., associating dentist with pain due to past
(e.g., pain behavior may be positively reinforced
which may itself increase pain perception).
The role of affect (emotion)
Worry and anxiety relate to pain perception.
Acute pain increases anxiety.
Chronic pain treatment ineffective increases
anxiety increases pain.
Fear of pain and fear avoidance beliefs.
Exacerbate existing pain and turn acute pain to
The role of cognition
Pain has different meanings to different
Attention to pain can increase perception of pain
Distraction reduces pain
Pain behavior and secondary gains.
The way a person responds to pain can increase
or decrease pain perception.
Psychosocial Factors in the Experience of Pain
As people get older, there is a progressive
increase in reports of pain and a decrease
in tolerance to pain.
A normal consequence of aging? Or do other
factors (overall health, coping resources,
differences in socialization) account for
Women report more frequent episodes of pain than
men, including more migraines, tension headaches,
pelvic pain, facial pain, lower back pain.
Gender differences already apparent by adolescence
and in medicine’s differential response to the pain
reports of women and men.
Gender difference in pain physiology? Certain
analgesics may be more effective for women than for
Is There a Pain-Prone Personality?
Acute and chronic pain sufferers show elevated
scores on two MMPI scales:
Hysteria (tendency to exaggerate symptoms and
use emotional behavior to solve problems).
Hypochondriasis (tendency to be overly
concerned about health and to over report body
Chronic pain sufferers also score high in depression.
Is There a Pain-Prone Personality?
Report high levels of pain, feel they have little
control over their lives, and are extremely inactive.
Interpersonally distressed patients
Perceive little social support and feel other people in
their lives don’t take their pain seriously.
Report lower levels of pain and distress and
continue to function at a high level.
Groups differ greatly in their
norms for the degree to which
suffering should be openly
expressed and the form that pain
behaviors should take
Pain tolerance versus pain
Pain tolerance: The greatest level of pain that a
subject is prepared to tolerate
Pain threshold: The least experience of pain that
a subject can recognize.
Electromyography (EMG) — assess the amount
of muscle tension experienced by pain sufferers
Indicators of autonomic arousal — using
measures of heart rate, breathing rate, blood
pressure, etc. to measure pain
Physiological measures are not as reliable or
valid as self-reports or behavioral observations.
Myths about Children and Pain
Young infants do The CNS of a 26-week-old fetus
not feel pain possesses the anatomical and
neurochemical capabilities of
Children easily become Less than 1% of children treated
addicted to narcotics with opioids develop addiction.
Children tolerate pain better Children's tolerance for pain
than adults increases with age
Children are unable to tell Children may not be able to
you where they hurt express their pain in the same
manner as adult
Children become accustomed Children exposed to repeated
to pain or painful procedures painful procedures often
experience increasing anxiety
Children will tell you when Children may not report pain
they are experiencing pain
Children's behavior reflects Children are unique in their ways
their pain intensity of coping.
Texas Children’s Cancer Center, Texas Children’s Hospital. Houston, Texas.