1. Unraveling the Mystery of Chronic Pain
John D. McKellar, PhD
Department of Veteran Affairs and
Stanford University

2. Understanding Chronic Pain
Acute versus Chronic Pain
Specificity Theory
Gate Control Theory
Additional factors that influence pain

3. Acute vs Chronic Pain ACUTE CHRONIC A warning sign
Time-limited, diminishes as healing occurs
Cause usually known, identifiable
CHRONIC
False alarm, not a signal of injury
Persists beyond 90 days, expected healing
Observable physiological signs may be absent

4. Theories of Pain Pain is basic to human experience
Provider’s theories about pain are primarily based upon the provider’s experience
The challenge for pain theory is to account for wide variety of human pain experiences

5. Specificity Theory Oldest theory of pain, physical pathology = pain
Rene Descartes Pain Illustration 1644

6. Specificity Theory Pain Intensity = Physical Pathology
Pain Center
Site of
Injury
Spinal Cord
Pain Intensity = Physical Pathology
No Additional Influences
Oldest theory and still the most widely held by patients and providers

7. Specificity Theory Limitations
Many people continue to experience pain well after an injury has healed.
People with identical injuries report vastly different levels of pain.
Subjects in experimental pain studies report vastly different levels of pain to the same stimulus.

8. Specificity Theory Negative consequences
Providers question patient’s report of pain when they cannot see evidence of damage
Patients assume that the presence of pain indicates that something is very wrong (which increases pain perception)

9. Gate Control Theory
Pain perception is a function of sensory input from the body (ascending pathways) and perceptions from the brain (descending pathways).
The “gate” is located within the spinal cord (dorsal horn) and involves input from body and brain operating simultaneously- the gate opens or closes.
Factors that open the gate increase pain, factors that close the gate decrease pain- as with a volume knob.

10. Gate Control Theory Site of Injury Gate (open/closed) Emotion Center
Pain Center
Emotion Center
Thought Center
Site of Injury

11. Gate Control Theory Factors that Open the Gate Negative Emotions
Depression, anxiety, stress
Negative Thoughts
“I can’t take this pain anymore”
Focusing Attention on Pain
Absence of pleasant activities, unemployment

12. Gate Control Theory Factors that close the gate Positive emotions
States of Relaxation
Guided imagery, Meditation,
Yoga, etc.
Attention directed away from pain
Recreational activities, positive distraction, etc

13. Gate Control Theory Site of Injury Situation/ Behavior/ Physical State
(open/closed)
Pain Center
Emotion Center
Thought Center
Site of Injury
Situation/
Behavior/
Physical State
Thoughts
Emotions

14. Gate Control Theory Example #1 Opening the Gate
Two patients attend a dental appointment…..

15. Gate Control Theory Closing the Gate
Example: An offensive lineman on the SF 49ers was seen rolling on the ground in pain at the close of a play….

16. The Gate Control Theory provides us with ways to help patients
“turn down the volume” on their pain!!

17. BioPsychoSocial Model of Pain
Environmental/Social
Factors
Pain Responses
Psychological
Biological
Behavioral/Social

18. Biopsychosocial Variables Associated with Chronic Pain:

19. Beliefs About Pain Hurt vs. Harm – Pain as a Mystery –
Pain Self-Efficacy –

20. Catastrophizing
Catastrophic thoughts involve thinking the worst about pain or its implications
“this will go on forever,” “my pain will never stop,” or “nothing can be done to improve my pain.”
Extremely prevalent and problematic, BUT appears to decrease in response to CBT-CP.

21. Avoidance
Avoidance of activities and people is a hallmark symptom of CP
“Disuse syndrome”
Avoidance of social or recreational activities can lead to isolation and depression

22. Fear or Movement/Re-Injury
Onset of
Pain
Painful experiences
Fear of movement
or injury
Avoidance
Disability
Disuse
Depression
No Fear
Approach
Recovery
Catastrophizing

23. Solicitous Loved One
Individuals highly responsive to a patient’s pain/pain behaviors actually increase a patient’s level of pain (compared to spouses/partners who suggest helpful but distracting ways to cope with pain)
If demonstrations of increased pain garner additional attention/assistance, there may also be secondary gains
Solicitous Spouse Study-

24. Social Constraints
If “solicitousness” is at one end of a social dimension then “constraint” is at the other
Social Constraint involves preventing expression about health problems such as pain
This can happen from significant others or from providers

25. Summary Acute versus Chronic Pain Specificity Theory
Gate Control Theory
Additional factors that influence pain: thoughts, behaviors, social