Mini-Science 2012 Q&A: “Pain, friends, sex and your mother” and “Why a broken heart really does hurt”

Mini-Science logoAt the conclusion of each Mini-Science lecture, audience members submit their questions to the evening’s presenter, who answers as many as possible on the spot. Some of the best answered or unanswered questions are sent to the presenter for posting here. Here are questions from the third and fourth lectures in the series.

From Professor Jeff Mogil’s talk, “Pain, friends, sex and your mother: complexity and opportunity in pain science and treatment”, April 11, 2012:

Q: How reliable is measure of pain using reactions to pain? Can peer pressure affect the undergraduate’s rating of pain? Was the number of times the mice writhed an accurate measure?

A: One question seems to be in relation to our study where we tested people alone vs. in a dyad. You are right, it would affect their reporting of pain if they were allowed to talk to each other, but they weren’t. In fact, we made a ruse in this situation, we pretended that we needed to test twice but we were running out of time so we would test two people together. They were given instructions to look straight ahead and not to talk. So peer pressure did not play a role. In terms of mice writhing, this is a complicated question. It is a reflex, and some people have a problem with measuring reflexes as a measure of pain in animals because human pain is not reflexive at all. You can show that humans have pain reflexes, but back pain and headaches are not pain reflexes they are something else entirely. People have started developing new measures. One of those is the facial expression system. People have started looking fancier methods where they are basically asking the animal to tell us about the pain. So suffice it to say that the system isn’t perfect but it is getting better.

Q: Does the fact that women perceive pain differently result from misdiagnosis by male practitioners and how about other diseases? Will patients report different amounts of pain to female vs. male doctors?

A: In regards to the first question, you are right, there is an issue with heart-attacks and cardiovascular events being much more likely to be painful in men than in women, which leads to people missing that it is happening in women leading to more severe consequences for women. No one believes that has anything to do with pain-sensitivity per se. It is a sex difference, but it appears to be a sex difference in the actual heart not in the brain.

There have been very few studies in regards to pain reports to male and female doctors. However there are studies with differences in pain reports to male and female experimenters. The first couple of studies came out with the result that you might imagine. Men reported lower levels of pain if the experimenter was a woman. Women reported higher levels of pain if the experimenter was a man. A study also tested differences depending on how the experimenter was dressed. Men reported even lower levels of pain to provocatively dressed women, and the provocatively dressed men elicited higher pain reports in women. However, more studies were done that did not conclude the same things, so now we don’t really know.

Q: Should we prevent families from visiting patients if it increases their pain? Should I stop going with my 9 year old son to his vaccinations?

A: There is a critical study that showed, in addition to the free mouse spending more time with the “mouse in pain”, the more the free mouse did that, the less pain the “mouse in pain” was in. The nursing behavior resulted in pain analgesia. That means yes, you should be accompanying your 9 year old to the emergency room. What is a bad idea is semi-private rooms in hospitals where both patients are in pain. A good way to test this would be to go to an army barracks with women recruits, it would be reasonable that every so often one of the recruits would have a migraine. In a dorm, if you have a migraine you go to your room. But in an army barracks all she could do is lie in her bunk. I bet you would get other women with migraines after the first woman got her migraine.

Q: Are there sex differences in regards to response to medication such as aspirin and Tylenol?

A: Most data suggests that women are more sensitive to morphine and drugs like it. This is an example where humans are completely different from animals. In animals (including monkeys), the males are more sensitive to morphine.

From Professor Jennifer Bartz’s talk, “Why a broken heart really does hurt”, April 18, 2012:

Q: Is there any indication that premature babies, or other babies separated from their mothers for considerable time in hospital, manifest separation pain?

A: I am not aware of any research that has definitively linked prematurity to separation pain sensitivity. Prematurity is a complex issue with many causes and it would be important for any such research to parcel out the causes of prematurity on pain sensitivity form the experience of prematurity itself. That said, researchers—including some at McGill like Dr. Michael Meaney and his colleagues—are actively studying the long terms effects of prematurity and other pre- and post-natal issues on neurodevelopment and behavior.

 With respect to the broader question about babies being separated from their mothers, as noted during the talk, mammalian infants have a very long period of infancy and require sustained care to ensure their survival. According to Attachment Theory, we have a built-in “attachment behavioral system” that promotes the infant’s survival by facilitating caregiver closeness and protection. A core feature of the attachment system is the notion of internal working models, which contain information about close others’ reliability and availability to meet one’s needs for security; while these schemas start out reflecting expectations about the caregiver, overtime they are used as templates to guide more general interpersonal perceptions, expectations, and behaviors. Research on Attachment Theory has shown that when the caregiver is unavailable or inconsistently available infants can develop insecure internal working models—i.e., the general expectation that mom is not available, or is inconsistently available, to meet one’s needs for felt-security; these insecure working models are then applied to new relationship experiences biasing expectations (e.g., “close others are unreliable”) and, in response to the question above, making people predisposed to be rejection sensitive.

 Critically though, although early caregiving experiences can have a significant impact on people’s interpersonal expectations, their impact is not written in stone. Studies show that infant and adult attachment styles are only moderately correlated, which suggests that attachment representations are formed in early childhood but they are adjusted or modified to incorporate new relationship experiences. Thus, even if a child experiences instances of neglect in early life, it is still possible to ameliorate the effects of these experiences through exposure to positive social experiences and supportive others.

Q: If social pain is to encourage us to reconnect with others, why is there so much disconnection in the world? Do we need to feel a lot of pain to bring us together?

A: This is a great question. First, I think it’s important to make the distinction between social disconnection (isolation), and social difficulties (not getting along with others, being in an unsatisfying relationship, etc.). The former is characterized by an absence, and the latter is characterized by the presence, of social relationships (albeit dissatisfying ones). I would say that the latter is probably more common than the former—that more people experience difficult relationships than live in a state of complete isolation/disconnection.

Second, I do not think that the reason people experience social disconnection and/or interpersonal strife is because they do not experience enough pain, but rather that experiencing pain is part of the solution—but not the whole solution—to being socially well connected. Social pain functions to motivate people to reconnect with others, but it does not necessarily tell people how to do this or, more precisely, how to do the well. An analogy can be made to hunger: although the aversive state of hunger motivates us to eat, it does not motivate us to eat good, healthy food. By the same token, although people may experience pain following rejection and/or isolation, and are motivated to reconnect, they may not always use best strategies to reconnect with others and thus may continue to feel interpersonally dissatisfied or isolated.

Q: When one takes a drug to ease social pain isn’t that what drug addicts do?

A: I’m not sure that taking a drug to ease social pain is analogous to addiction but I agree that the acetaminophen study raises some important questions about (social) pain management.

 This question is related to the discussion during the Q & A period about ‘basic’ and ‘applied’ research objectives. The goal of the acetaminophen study was to provide evidence that our capacity to experience of social and physical pain rely on the same (or at least overlapping) neural mechanisms. Recall that one hypothesis generated from this theory is that factors that influence one kind of pain should influence the other kind of pain; the acetaminophen study sought to test this hypothesis by looking at whether a drug that is known to alleviate physical pain also affects social pain. This is a basic science question about identifying the biological mechanisms of social pain. Although the results from this study could have applied value I do not think that identifying a cure for social pain was the goal of the study. As the authors state, “Our findings do not warrant the widespread use of acetaminophen to cope with all personal problems”.

 Indeed, a fundamental assumption of the social-physical pain overlap theory is that our capacity to experience social rejection/disconnection as painful is adaptive because pain is an aversive state that should motivate people to reduce that state by reconnecting with others. An inability to experience social pain would, in fact, be maladaptive because people would not be motivated to change their behavior, or their circumstances. For example, someone who was unable to experience social pain would, in theory, be more likely to remain in a state of isolation or in an abusive relationship, both of which would be maladaptive for the individual over the long run.

Q: What are the dosage, brand, and funding source of that acetaminophen study?

A: Participants took one 500-mg acetaminophen pill in the morning, and another 500-mg pill just before going to sleep. The study used the generic formulation, not Tylenol, and was funded by the National Institute of Mental Health. There is no indication of pharmaceutical funding for this study.

 Q: What is acetaminophen’s mechanism of action?

A: The authors state that the precise mechanism by which acetaminophen alleviates pain is unknown but that it is widely believed that the analgesic effects are achieved via central, rather than peripheral, nervous system mechanisms; based on this, and the knowledge of brain regions implicated in physical and social pain, they conclude that acetaminophen may reduce the experience of social pain by attenuating neural activity in brain regions known to play a role in physical and social pain processes. An interesting point about mechanism that the authors note is that acetaminophen has a relatively short half-life (approximately 4 hrs). Because of this, they argue, it is unlikely that acetaminophen had a cumulative effect in reducing social pain but rather that effects of acetaminophen were likely due to a combination of i) not feeling hurt and ii) increasing people’s ability to generate alternative—and more benign—explanations for being excluded.

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