Lecture 19:Pain Dr.Reem AlSabah

Dr. Reem Al-Sabah

Faculty of Medicine

Psychology 220

What is pain?

Pain is “an unpleasant sensory and emotional experience associated with actual or potential tissue damage or described in terms of such damage.”

(The International Association for the Study of Pain)

Pain is an almost universal experience, yet difficult to define.

Clinical Pain: Pain that requires some form of medical treatment.

Pain is the most common reason people seek medical treatment.

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 sleep.

A warning sign that something is wrong resulting in protective behavior.

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 pain.

The Pain Pathway

1. Transduction

2. Transmission

3. Modulation

4. Perception

Transduction The process by which afferent nerve endings translate

noxious stimuli (e.g., a bee sting) into nociceptive impulses.

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.

Transmission 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-fibers.

Modulation

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.

Perception 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

Biomedical framework

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 organic pain

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 sensory channel.

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 gate.

The role of multiple causes

The GCT suggests that many factors are involved in pain perception, not just a singular physical cause.

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 fibers)

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, relaxation)

Behavioral factors (focus, concentration, distraction, or involvement in other activities)

Psychosocial aspects of pain

Pain

Operant conditioning

Anxiety

Fear

Secondary

gains

Pain behavior Catastroph

-izing

Attention

Self-efficacy

Meaning

Classical conditioning

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

Subjective-affective-cognitive processes

The role of learning

Classical conditioning

(e.g., associating dentist with pain due to past experience).

Operant conditioning

(e.g., pain behavior may be positively reinforced which may itself increase pain perception).

The role of affect (emotion)

Anxiety

Worry and anxiety relate to pain perception.

Acute pain increases anxiety.

Chronic pain treatment ineffective increases anxiety increases pain.

Fear

Fear of pain and fear avoidance beliefs.

Exacerbate existing pain and turn acute pain to chronic.

The role of cognition

Catastrophizing

Rumination

Magnification

helplessness

Meaning

Pain has different meanings to different people

Attention

Attention to pain can increase perception of pain

Distraction reduces pain

Behavioral processes

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

Age

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 age-related differences?

Gender

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 men.

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 symptoms).

Chronic pain sufferers also score high in depression.

Is There a Pain-Prone Personality? Dysfunctional patients

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.

Adaptive copers

Report lower levels of pain and distress and continue to function at a high level.

Sociocultural Factors 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 threshold

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.

Measuring Pain Psychophysiological Measures

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.

Measuring Pain Behavioral Measures

Pain Behavior Scale

Self-Report Measures

Pain rating scales (numerical ratings or a pain diary)

Standardized pain inventories

McGill Pain Questionnaire (MPQ): sensory quality, affective quality, evaluative quality of pain

Pain Intensity Scales

Myths about Children and Pain Myth Truth

Young infants do

not feel pain The CNS of a 26-week-old fetus possesses the anatomical and neurochemical capabilities of sensing pain

Children easily become

addicted to narcotics

Less than 1% of children treated with opioids develop addiction.

Children tolerate pain better

than adults

Children's tolerance for pain increases with age

Children are unable to tell

you where they hurt

Children may not be able to express their pain in the same manner as adult

Myths (Cont.) Myth Truth

Children become accustomed

to pain or painful procedures

Children exposed to repeated painful procedures often experience increasing anxiety

Children will tell you when

they are experiencing pain

Children may not report pain

Children's behavior reflects

their pain intensity

Children are unique in their ways of coping.

Texas Children’s Cancer Center, Texas Children’s Hospital. Houston, Texas.