Lec. 1 (intro)

Question 1

Why is pain a course in psychology?

Answer 1

• pain is a perception
• pain is an emotion
• pain is a strong (the strongest?) motivator of behaviour
• pain importantly affects psychological health and well-being
• pain is more “psychological” than other sensations or disease states (pain is very affected by mood); the correlation between the intensity of the stimulus and the intensity of the perception is weak
  People think psychological = pain is in their head. Just because something is affected by psychological factors doesn’t mean it’s all in the head.

Question 2

Why do people inflict themselves pain?

Answer 2

• Proving themselves to be strong (presumably men when women are watching)
• Ritualistic reasons (ex. passage into adulthood)
• Something is to be gained (ex. muscles, strength, or simply tolerance to pain)
• Artistic/performance reasons

Question 3

The 2 nails

Answer 3

• One man had a workplace accident where he saw a nail go right through his shoe, and began to be in immense pain. It turned out that the nail went between his toes, and that the man was in fact not injured. The pain wasn’t caused by any physical factors, but by psychological ones.
• Another worker accidentally shot himself in the mouth with a nailgun (a nail went through his skull), but he didn’t notice it and thought he was uninjured, until he went to the dentist because of a mild toothache (nail was shown on X-ray)

Question 4

Inguinal hernia

Answer 4

Part of the intestine pokes out of a hole in the muscle/ abdominal wall. The surgery to treat it is very hard to recover from.

Question 5

Example of feeling pain with no tissue damage (hernia story)

Answer 5

Expecting/fearing the implications/consequences of the injury itself can lead to pain, which can then disappear rapidly if it is made clear that there is no injury, or at least none of the frightening implications that the injury was expected to have.

Question 6

Other possible modulators of pain (not psychological) - problems with civilians vs. soldiers study

Answer 6

In Beecher’s study, the civilans asked for morphine more often than the soldiers, for the same injuries (which caused more pain for the civilians). Beecher concluded that it represented the psychological modulation of pain. But there are other possible reasons for that result:
- Time since injury
- Age of patient
- Stress levels (stress can alleviate pain)

Question 7

Variability in OA patients’ pain levels

Answer 7

In patients shown to have osteoarthritis (OA) disease, a median of only 30% report pain, and in all patients with knee pain, a median of 30% have OA. This raises the question: is the OA causing the pain? The answer is that it probably isn’t, at least directly, because otherwise all OA patients would feel pain. OA might just be correlated/associated with pain. The real cause of pain is probably only psychological.

Question 8

Pain and the medical world

Answer 8

• Pain (back) is the #1 reason to seek health care. Pain is present in 5/10 complaints at family doctor visits: back, abdominal pain, sore throat, headache, leg pain. The patients go to the doctor because of symptoms (like pain), not because they think they have a disease.
• Pain is the #1 concern of patients with chronic disease (e.g., cancer, arthritis). People with cancer are less concerned about dying than living in pain.
• Despite what doctors learn in medical school, pain can kill (not directly, but it can, it makes life impossible).

Question 9

Prevalence of chronic pain

Answer 9

• Almost 50% of people have experienced chronic pain in their lives. This is one of the most prevalent pathological states.
• Almost 25% have chronic pain at any moment. Not just old people (but more frequent in old people).
• Point chronic pain: in some defined time period (ex. in the last year, in childhood, etc.). Compared to lifetime chronic pain. Both have a 25% prevalence in the population.

Question 10

Epidiomology

Answer 10

The study and analysis of the distribution, patterns and
determinants of health and disease conditions in a defined population.

Question 11

The epidemiologist’s bathtub and chronic pain

Answer 11

• Population: bathtub
• Prevalence: how full the bathtub is (proportion of the population suffering from chronic pain)
• Incidence: how many drops drip (how many new cases of chronic pain) in a certain amount of time
• Recovery: evaporation (the bathtub is getting less full: some people recover)
• Mortality: leakage (the bathtub gets less full: some people die)

Question 12

Importance of defining prevalence

Answer 12

In epidiomology, people try to cheat: activists want to make prevalence numbers to be as high as possible (to get more funds). Governments want to make them as little as possible (to not have to pay as much). The reference population influences prevalence.

Question 13

What matters in a study in pain?

Answer 13

Every decision the researcher makes is important:
- Age of sample (ex. is adolescence 12-18 or 14-17?)
- Definition of pain (or migraine if study is on migraine)
- Sample size
- Time frame (ex. measures are made over a year)
- Sample characteristics (ex. ration male-female)
One study is almost never enough to have a result you can infer to the population - you need a meta-analysis (combine studies to find average results)

Question 14

Prevalence of pain compared to other diseases

Answer 14

The top one chronic condition is back pain, and 4/10 most prevalent conditions are linked to pain (arthritis, migraine, Crohn’s disease).
Pain doesn’t get the notice/funding that it deserves compared to other deseases. One reason is that pain doesn’t kill you (morbidity doesn’t get as much attention as mortality). Another possible reason is that the word “pain” isn’t always visible in the name of the disease (ex. arthritis)

Question 15

Prevalence of pain by body part

Answer 15

• Head: 15% (mostly migraines)
• Lower back: 18%
• Knee: 16% (mostly arthritis)
  Medicine has specialties according to body parts. The prevalence of pain is pretty high in all body parts.

Question 16

Burdens of pain

Answer 16

• Social consequences, social isolation
• Family and marital consequences, problems with intimacy
• Sleep disturbances
• Disability (incapacity to do chores, work, hobbies…)
• Socioeconomic consequences, cost to government
• Emotional consequences (irritability, anger, anxiety, depression…). Pain changes people, often negatively.

Question 17

Back pain and disability

Answer 17

55% of people with lower back pain can’t do complex actions, and more than 50% of them can’t do basic actions (like stand, walk, eat, sleep, etc.). Lower back pain is especially debilitating, because the back supports the whole body.

Question 18

Global burden of disease

Answer 18

Study done by the WHO, which looks at different pains. They measure Years Lived with Disability (YLDs) and how comorbid people compare different experiences of pain (so how bad the pain is multiplied by how long it lasts). Back pain is seen as worse than blindness. Hedaches and back pain, knee pain and musco-skeletal pain, are seen as some of the biggest burdens to people.

Question 19

Pain and social functions

Answer 19

Around 80% of people with chronic pain need to postpone household duties, laundry, shopping, cleaning, yardwork, cooking… Between 60-70% of chronic pain patients postpone activities with their spouse or children, and almost 20% can’t get out of bed on some days. Chronic pain has a negative impact on 25% of (romantic) relationships.

Question 20

Comorbidities with chronic pain

Answer 20

The most common ones are difficulty sleeping + lack of energy + drowsiness + difficulty concentrating. Sometimes the comorbidity is worse than the pain (esp. sleep difficulties).

Question 21

Reasons for comorbidities

Answer 21

One possibility is that pain is causing these other conditions (ex. sleep problem).Or it could be that the other conditions exacerbate/cause the pain. The third option is that both the pain and the condition are caused by a third problem. For sleep, there is evidence for the 3 options.

Question 22

Chronic pain and suicide risk

Answer 22

The proportion of people with suicidal thoughts/ideations, plan, and attempt, are higher in chronic pain patients than in the general population (for suicidal ideation in lifetime, it’s 19% against 9%)

Question 23

Effects of chronic pain on lifespan

Answer 23

Pain doesn’t kill directly, but it affects mortality in some indirect ways that are still studied. Data shows us that widespread pain has the biggest effect on lifespan 8reducing it dramatically comapred to regional pain and no pain).

Question 23

Kaplan-Meier plot

Answer 23

Non-parametric plot that is used to estimate the survival function from lifetime data (ex. lifespan of people with vs. without chronic pain)

Question 24

What are chronic pain patients dying of?

Answer 24

Same causes as everyone else. The most common ones are:
- Cardiac arrest (cardiovascular disease are the most common ways to die)
- Cancer
- Chronic pulmonary disease
Together, those make up 90% of all deaths. All these patients die of the same thing but pain makes them die more easily.

Question 26

Economic burdens of pain on the country’s GDP

Answer 26

The estimated cost of back pain in the US is 200 billion dollars. Pain costs around the same amount of money in the US as heart disease, cancer, and diabetes combined. Pain is the most expensive disease to the US, around the same amount than the budget of the US department of defense. More pain cases = more need for doctors. Pain also causes workers to lose in productivity, costing the company.

Question 27

Pain in Abrahamic religions

Answer 27

• Pain as a punishment for sin (old testament: childbirth is painful for women as punishment for Eve’s original sin)
• Pain as redemption: new testament, Jesus suffers to redeme humanity as a whole
• Pain as (personal) atonement: in the Quran, if a Muslim is sin-free, he feels no pain. Pain is inflicted by Allah to cleanse the Muslim of his sins.

Question 28

Etymology of pain

Answer 28

• Greek: “poine” (penalty, payment: Poine is the Greek spirit of punishment) -> Latin: “poena” (pain, punishment, penalty) -> Anglo-French: “peine”
• Proto-Indo-European: “delh” -> Latin: “doleo” (I grieve for, lament, deplore) -> Old French: “dolor”
• In English, the word “subpoena” (order issued by the court to give a testimony in court - not complying means having to pay a fine) still uses the latin word.

Question 29

issued by a government agency, most often a court, to compel testimony by a witness or production of evidence under a penalty for failure.

Answer 29

1. Aristotle (4rth century BCE): pain is an emotion, in the heart (he was right about the emotion, not about the heart)
2. Galen (2nd century AD, considered the 1rst physician): pain is a sensation, in the brain (he was mostly right, except that pain is not only a sensation)
3. Avicenna (Arab doctor, beginning of 11th century): pain is an independent sensation from touch/temperature (he was right). At the time, it was thought that pain was caused by an excess of pressure or temperature.
4. Descartes (beginning 17th century): there exists a “pain pathway” from the body to the brain (he was right but couldn’t know about the exact pathway)

Question 30

Theodicy

Answer 30

The “vindication of God”; the answer to the question of why a good God permits the manifestation of evil. Why does God allow pain?

Question 31

Utilitarism

Answer 31

Tries to answer the question: what decisions are ethical? The answer is to do a cost/benefit analysis, with cost = pain and benefit = pleasure (but for whom?).

Question 32

The principles of Utility (Jeremy Bentham, 18-19th century)

Answer 32

1. Recognizes the fundamental role of pain and pleasure in human life
2. Approves or disapproves of an action on the basis of the amount of pain/pleasure brought about (the consequences of the action)
3. Equates the good with the pleasurable and evil with pain
4. Asserts that pleasure and pain are capable of quantification - and hence of measure

Question 33

Pian and the mind-body problem

Answer 33

The mind-body problem: dualism (ex. Cartesian) vs. monism.
Phantom limbs were thought to be a proof of dualism: people who lost a limb could still feel pain in their absent limb, meaning that the limb could survive physical destruction (and thus the whole person could too when the body died)

Question 34

Pain and the problem of “other minds”

Answer 34

It’s impossible to know if someone else has a consciousness or what goes on in their mind if they have one. I can never know if someone else truly know what pain is, or if we feel pain the same, etc. We don’t feel the pain of others, so to us, there’s no experience of pain. And since pain is a personal experience, there is no pain. How can there be pain when you yourself don’t feel pain?

Question 35

Pain and animal rights (Singer, 1975)

Answer 35

The fundamental interest that entitles a being to equal consideration is the capacity for suffering and/or enjoyment or happiness. We need to take the lives/right of animals seriously to the extent of them being capable of being happy/in pain. But how to know if a living being can feel pain?

Question 36

Pain and human rights

Answer 36

The declaration of Montreal (2010) by the International Association for the Study of Pain (IASP) declared that the following human rights must be recognized throughout the world:
Article 1. The right of all people to have access to pain management without discrimination.
Article 2. The right of people in pain to acknowledgment of their pain and to be informed about how it can be assessed and managed.
Article 3. The right of all people with pain to have access to appropriate assessment and treatment of the pain by adequately trained health care professionals.
Those aren’t laws enforced by countries, but an idea of how pain should be managed in the world.

Question 37

Opioid Consumption by Country (2019)

Answer 37

Canada, Switzerland, and Germany are the top 3 opioid consumers in the world. The majority of countries in the topm of the list are in Europe. Poorer countries in South America, Africa and Asia, like Peru, Colombia, The Philippines, Chile, Egypt, Venezuela, etc. consume virtually no opioid compared to Europe. They either don’t have enough opioids or don’t use them - they suffer through pain.

Question 38

Pain in Art

Answer 38

Pain is very present in art. For example, Frida Kahlo broke her back in a bus accident, which caused chronic pain for the rest of her life. She painted herself in pain in her painting “The Broken Column”

Question 39

Pain and the Law

Answer 39

• Compensations for pain/suffering: after an accident, many people appear with a neck brace (and supposedly have whiplash) to get a higher compensation. There is a need for objectively diagnosing the levels of pain in a person.
• Work accidents can lead to compensation from the company (paid recovery time)
• The opioid crisis

Question 40

The old definition of pain

Answer 40

“An unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage.”
The definition of pain is very hard to come by. Before that definition (1979), every dictionary had a different definition, and they were all debatable.

Question 41

Is pain always unpleasant? Examples of pleasant pain

Answer 41

• Masochism: enjoying pain, often in a sexual context. But half of masochists asked say they would rather be able to enjoy sex without feeling the pain. There is a trade-off: unpleasant pain to pleasant orgasm.
• Tanning, sauna, massage
• Eating spicy foods
• Exercise: before and after (DOMS: soreness, it feels good because we know that no pain = no gain). Still, we would rather be able to exercise without feeling pain.
• Self-harm: the idea is less about feeling pain as it is about controlling the pain. There is also a trade-off, like for masochism and exercise.
• Pain in one place can make pain in another place less unpleasant (trade-off, the pain itself isn’t pleasant)

Question 42

Pain as a sensation?

Answer 42

In the Middle Ages, it was thought pain was jsut “high-intensity touch”. However, there is a mismatch in the stimulus-response reaction that doesn’t exist in other sensations. Also, while you habituate to other senses, you become more sensitive to pain (habituation vs. sensitization - for example you stop hearing the fridge humming because the brain doesn’t want you to use your attention to stimuli that aren’t useful anymore. Pain doesn’t do that. The longer a pain stimulus is there, the more you notice it)

Question 43

Pain as an emotion and homeostatic emotion

Answer 43

• Pain activates brain areas related to emotions
• Pain can be considered a homeostatic emotion (drive state) like thirst, hunger, sleepiness, need to breathe… Some people have argued that pain is the drive state that overcomes other drive states (ex. during torture, you forget about hunger and thirst). It is cannot be ignored.

Question 44

Adequate stimulus for Pain

Answer 44

Adequate stimulus: the stimulus that can evoke a response (ex. photons for vision). For pain, there are many. For example, there is inflammatory peptides, environmental irritants, noxious mechanical stimuli, noxious cold/hot temperatures, pungent natural compounds (ex. onions), cell rupture (which releases a pain-causing chemical)

Question 45

Problem with “described in terms of such damage”

Answer 45

This phrase is here because there is a whole class of pain disorders (neuropathic pain) where there is no tissue damage (ex. memory of pain). It feels like tissue damage. If the phrase wasn’t there, it would allow people to put off people who feel pain without tissue damage.
The problem is that some people aren’t able to describe the pain. Describe implies verbal abilities. Just because you can’t describe something doesn’t mean you can’t perceive it.

Question 46

The new definition of pain

Answer 46

An unpleasant sensory and emotional experience associated with, or resembling that associated with, actual or potential tissue damage.
Only one change: got rid of the word “describe” and made sure the definition doesn’t imply being able to verbally describe the pain.

Question 47

What is pain not?

Answer 47

• a somatosensation (anesthesia and analgesia aren’t the same)
• emotional pain (most of the time, it is different in the brain, but there are exceptions)
• suffering
• disability (pain can cause disability but disability isn’t always linked to pain)
• pain behavior (pain behavior doesn’t always occur in instances of pain. You can’t tell if someone’s in pain just from their behavior)
• nociception (nociception is the biology that produces the perception of pain - it’s unconscious, while pain is the final conscious perception)

Question 48

Physical vs. emotional pain

Answer 48

Most of the time, they are represented differently in the brain. Except…
- Social rejection causes inflammation
- Social suffering activates the brain’s “pain matrix” (ex. after a breakup). However this is only true if you’re not really precise by what you mean by “pain matrix”. Different definitions yield different results
- Acetaminophjen reduces social pain

Question 49

Thermal grill illusion

Answer 49

Bars of cool and warm metal alternate. If you put your whole hand on it, you feel burning (or burning cold). It’s impossible to let your hand stay on it for long. There is no nociception (at least not in the hand), but there is pain (an illusion caused by a mechanism in the cortex). The somatosensory system is not designed to detect such tight differences between hot and cold. And so when the brain experiences alternating hot-cold just within the span of your fingers, it gets confused and confusion of the sensory system defaults into pain.

Question 50

Fordyce’s behavioral model of pain

Answer 50

Nociception is the core, which then produces pain, which can cause suffering, that could finally lead to pain behavior. There is the question of whether suffering is a necessary step, however the point of this model is to show that these steps are different concepts, linked to each other but not necessarily implying each other. They happen on different levels. The more you advance through the steps (the closer you are to behavior), the more it depends on contextual factors (ex. personality)

Question 51

Evolutionary explanation for acute pain

Answer 51

Acute pain: from seconds to minutes. It is helpful to prevent tissue damage (or further damage). It’s goal is to prevent dying, for example from infection (which is the number 1 cause of death across animals, including humans before antibiotics). It is also a way to learn about the environment, it acts as a teaching signal (infantile amnesia here has no incidence, because it’s only for episodic memories; not procedural or semantic ones).

Question 52

Evolutionary explanation for tonic pain

Answer 52

Tonic pain: from hours to weeks. It exists to motivate the animal to rest and recover after an injury. Your body doesn’t want you to move, so that it can heal properly.

Question 53

But why does chronic pain exist?

Answer 53

The truth is that it has no adaptive significance (no evolutionary explanation). It’s pathalogical. For example, arthritis, a chronic condition, makes people not want to move, but they actually should move to prevent further deteriorating of their joints.

Question 54

Congenital Insensitivity to Pain

Answer 54

An extremely rare condition in which a person can’t feel pain, formerly known as Hereditary Sensory Neuropathy type IV (sometimes associated with anhidrosis, when you can’t sweat - it’s then called CIPA). For example “the human pincushion”, a performer in the early XXth century, that would put needles in his skin for show. People with this condition mostly die young from infection. It is dangerous: babies bite out their tongues, people can’t feel when they’re burning themselves on accident, they don’t let their wounds heal properly, they don’t adjust their positions in ways that prevent injury…

Question 55

The lumping vs. splitting problem

Answer 55

When talking about any problem, you can either split it into different things to study independently, or you can look at what links the different things (what they have in common), to study as them one thing. A lot of problems in the world have this in common: people not knowing whether to lump or split. How to split pain in different problems that we can study independently?

Question 56

Ways of splitting the pain problem: duration

Answer 56

Acute-to-chronic pain transitioning. Traditionally, the distinction between acute and chronic pain has relied upon an arbitrary interval of time from onset; the most commonly used markers being 3 months since the initiation of pain. Others have placed the transistion at 12 months, 30 days… Others still think that there is another category, “subacute pain”, that lasts from one to six months. A popular alternative definition of chronic pain is “pain that extends beyond the expected period of healing. But what is the expected period? It could be different for everyone. Or maybe the wound didn’t heal correctly, and so the chronic pain is justified. Acute pain either goes away or becomes chronic, but what turns it into chronic pain, if there even is anything that does?

Question 57

Ways of splitting the pain problem: pain etiologies (examples)

Answer 57

• 1rst etiology example makes the difference between acute and chronic pain, then further subdivises chronic pain into nociceptive, neuropathic, visceral, and mixed. Neuropathic pain is then separated into 2 categories according to its origin: PNS or CNS.
• 2nd example (Costigan et al.): split pain into nociceptive, inflammatory, dysfunctional, and neuropathic. For each type, the duration and intensity of the pain following non-noxious, noxious, and highly noxious stimuli is different.

Question 58

Ways of splitting the pain problem: location

Answer 58

• Superficial pain (skin pain, ex. slicing, scratching, pressure, stretching…)
• Deep pain (muscle, joint, bone)
• Visceral pain (poorly localized, and sometimes feeling like superficial pain)
• Neuropathic pain
• Phantom limb pain
  For the last 2, we don’t really know where the pain is “located”, beacause the skin/organs are not injured, and it’s hard to trace back the origin of the damaged or problematic nerves.

Question 59

Symptoms of pain disorders

Answer 59

Most chronic pain patients have more than just spontaneous pain. There is some evidence than the other sensations that accompany it have different biological underpinnings, that’s why we split the problem:
- Spontaneous pain
- Evoked pain
- Paresthesia /dysesthesia
- Numbness
- Paradoxical thermal sensations
- Aftersensations

Question 60

Spontaneous pain

Answer 60

Pain that appears without any noxious stimulus. Could come from a previous injury. It comes from the inside.
- Continuous: always there.
- Paroxysmal: intermittent.
Spontaneous pain is necessary to be diagnosed with a pain disorder.

Question 61

Evoked pain (pain hypersensitivity)

Answer 61

Caused by external stimulus. 50-70% of chronic pain patients have pain sensitivity (added to the spontaneous pain that everyone has). Types:
- Allodynia (from heat, cold, mechanical, vibration)
- Hyperalgesia (from heat, cold, mechanical, vibration)
- Static (ex. from pressing down on injured zone) vs. Dynamic (from stroking injured zone), biology is different (can’t lump the problem)
- Activity-evoked (from moving)

Question 62

Allodynia vs. Hyperalgesia

Answer 62

• Allodynia: a stimulus that would not normally have been painful is painful; hypersensitivity
• Hyperalgesia: an already noxious stimulus is now highly noxious (causing more pain than it would usually do)

Question 63

Cervero’s view of pain hypersensitivity

Answer 63

According to Cervero, allodynia and hyperalgesia are the same thing: features of the fact that the curve of pain intensity in function of stimulus intensity shifts to the left (meaning that a less intense stimulus is needed to cause a certain level of pain. There is every reason to believe that they are caused by the same mechanism (pain hypersensitivity). They are just different names for different parts of the shift. Allodynia is the area where there is pain in case of an injury, but the pain curve is at 0 at the same stimulus level. Hyperalgesia is the area between the curves of injury pain response and normal pain response.

Question 64

Paresthesia vs. dysesthesia

Answer 64

• Paresthesia: a weird feeling that is not necessarily unpleasant
• Dyesthesia: a weird feeling that is always unpleasant (ex. pins and needles - not exactly pain but not a good feeling)

Question 65

Relative Frequency of Signs & Symptoms

Answer 65

• From interviews: most frequent complaints are of deep pain, ongoing pain, evoked pain, and activity-evoked pain.
• Dysesthesia symptoms: most frequent is tingling
• From physical examination: most possible symptoms (ex. pinprick hyperalgesia) are rare. The only one that is frequent is increased pressure sensitivity of deep tissues (tested by deep massage of the muscles).

Question 66

Sign vs. symptom

Answer 66

• Sign: something you can infer from a test you give to the patient (not questionnaires)
• Symptom: something that the patient tells you they have/feel

Question 67

Problem with animal research (when talking about frequency of signs and symptoms)

Answer 67

The fact that most frequent symptoms are from interviews, and signs from physical examinations are rare, means that what we can study in animals is only the rarest problems in humans. Also, we don’t really study numbness in animals, although it could be useful.

Question 68

Possible biological reason for pain hypersensitivity (squid experiment)

Answer 68

Until recently, the thought was that chronic pain had no adaptive function. One paper (2014) showed that injured squids could escape predators better than injured squids that lived in a tank full of anesthetics (this showed that pain could have some benefit for the squids). The authors speculate that it has to do with vigilance. Injuries make you more susceptible to being predated, so you don’t take as many risks.

Question 69

Pain and vigilance, relevance to humans

Answer 69

In evolutionarily primitive times, humans were preys, and needed to be hypervigilent when they were injured. The link between pain and hypervigilence can still be seen today: one of the major comorbidities of chronic pain is anxiety (which is a form of hypervigilence).