pain research

Six old papers for pain clinicians

We’re rather flighty beasts, us clinicians. From looking at the various ads for courses on the interwebs, it seems we’re all ready to jump on to the next newest thing. This same “what’s new” attitude is present in journals as well –  “these references are very old, are there newer ones you can use?”

Here’s a question: what happens to the old stuff? Is it outdated and useless? Do really well-conducted studies have a “use-by” date? Are older therapies always less effective than the new ones? What if this urge to “refresh” means we do actually throw the baby out with the bathwater?

Some of you will know that I’m keen on reading about the history of how we manage pain. I think it helps put some of our current dilemmas into perspective – and helps us understand “legacy” beliefs: things people believe based on old ideas about how our body works. It reminds me that some of these problems are not about research evidence, but about very human issues of political clout, social inertia, and legal factors (thinking of my recent post on the ” Dynasty of the Disc“.

So, today I want to talk about reading old papers. Papers written maybe in the 1960’s or 1970’s, 1980’s and 1990’s. Even from 2000 and on!

Here are some papers I think everyone working in pain and pain management should review:

  1. Melzack, R., & Wall, P. D. (1965). Pain mechanisms: a new theory. Science, 150(3699), 971-979.

The original paper, the one that ignited new ways of thinking about pain. Not a very long paper, and yes, many of the details proposed in this paper have been revised in light of new information, but the essential groundbreaking principles, distinguishing between nociception and pain, between peripheral and central mechanisms, of the modulation that occurs at every single synapse to and from the brain, of the need for us to consider OMG the brain!  This is the bit that really grabs my attention: 2. Fordyce, W. E., Fowler, R. S., & Delateur, B. (1968). An Application of Behavior Modification Technique to a Problem of Chronic Pain. Behaviour Research and Therapy, 6(1), 105-107.

This is the original paper by Fordyce and colleagues, demonstrating that by following the principles of operant conditioning, a person with persistent and disabling pain could return to daily life. It was extraordinary in that instead of focusing on pain – it focused on behaviour. Fantastic description of behaviour therapy in action.

3. Fordyce, W. E. (1988). Pain and Suffering: A Reappraisal. American Psychologist, 43(4), 276-283.  This is another paper by Fordyce, this time discussing distinctions between pain and suffering – he clearly articulates Loeser’s “onion rings” model which has been reproduced, revised, and possibly warped out of shape in various papers since (do a Google search and see what you can find!).

4. Engel, G. L. (1977). The need for a new medical model: A challenge for biomedicine. Science, 196(4286), 129-136. doi: The classic Engel paper, written for a psychiatry audience but with a far far wider impact on healthcare since. It’s really useful to read how Engel put this model together, the context at the time, and his ideas for how it might be used. The part that really gets me is how he considers the path from being a person to being a patient – that decision-making process to seek treatment which is rarely discussed (but is, I think, a crucial indicator of the expectations the person brings to a consultation)

5. Ignelzi, R. J., Sternbach, R. A., & Timmermans, G. (1977). The pain ward follow-up analyses. Pain, 3(3), 277-280. This paper is one of the very first to show that surgical approaches to pain management don’t provide the most wonderful outcomes, at least not in comparison with those who were participants in a pain management programme. I think it’s interesting because it shows the use of long term follow-up data to demonstrate effectiveness. Who would have thought two and three year outcomes would show such differences? And I wonder what would happen today?

6. I couldn’t resist this one: Fordyce, W., McMahon, R., Rainwater, G., Jackins, S., Questad, K., Murphy, T., & De Lateur, B. (1981). Pain complaint-exercise performance relationship in chronic pain. Pain, 10(3), 311-321. Why? Because as far back as 1981 we were seeing that advice to stop doing, or to use pain as a guide, was unhelpful. Perhaps it’s time we took this one on board?

There. Old papers. Old messages – perhaps ones we have still to adopt. Can we do better? Shouldn’t we do better? Should we stop trying to create new and groovy stuff and instead implement some of these really old principles?


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Correlation (even multivariate analysis) is not causation
I’ve been reviewing some of my PhD proposal (it has to be submitted by the end of this week), and considering the topic of coping.  Coping refers to ‘the strategies people use to manage pain and
its impact.’  It is one of the two main topics researched in psychological contributions to the pain experience, with the other being beliefs.

Although coping has been studied extensively, it has primarily been studied in people who are seeking treatment for their pain – and conclusions drawn about what constitutes effective coping is drawn from outcome studies looking at disability scores and correlations between the strategies used.  My question is whether that is the most adequate way of viewing the use of coping strategies, maybe it would be good to look at what people who have never had formal CBT treatment for chronic pain and see what they use.  Anyhow, this editorial by Mark Jensen reviews the tendency for even really experienced researchers to be tempted to use language that suggests causation when a conclusion can only be drawn about the tendency for two (or more) variables to systematically vary in relationship to each other.

He is discussing the findings of Karsdorp and Vlaeyen who examine the associations among psychological variables in a large sample of patients with fibromyalgia. They conclude that two types of avoidance strategy independently predict disability in this cohort of patients.

Jensen states ‘Psychological models of pain often hypothesize causal and mediational associations between different psychological factors or domains’ – the problem with this is that given the close relationships between some of these psychological variables, a ‘multivariate analysis that (1) estimates the associations between these variables and important criterion variables that also (2) controls for other psychological variables, will likely underestimate the importance of the psychological factor(s) being examined.’

What this means is that, in this study, two variables – catastrophising and pacing – were found not to predict disability when each was controlled for the other.  The authors of the study concluded that neither were significant predictors of disability – but what if the two varied systematically with each other because of some unidentified third variable?  Jensen suggests that perhaps depression may influence the use of both catastrophising and pacing, making it seem as though neither were individually significant, but actually confusing the finding because depression was not considered to be a mediating variable.

Jensen suggests ‘In short, negative results from studies that use analyses that control for psychological variables should not be used to draw strong conclusions about the lack of importance of any one variable.’

He finishes by stating ‘their finding that active avoidance is uniquely important in the prediction of disability when controlling for other psychological factors is an important one… but at the same time, one must be constantly vigilant to avoid viewing the findings from correlational studies as suggesting the presence of causal associations’.

He goes on to say  ‘the true (causal) importance of a psychological variable is best identified by experiments that systemically alter the variable in question, and then determine the subsequent effect of a change in the variable on measures of important outcomes.’

This is a timely reminder for us as consumers of research – we really do need to know about research methodology, or we may well skip to the ‘Discussion’ and miss the important details of how the researchers drew those conclusions.  Only then can we decide how much weight we put on the findings.

Jensen, M. (2009). Research on coping with chronic pain: The importance of active avoidance of inappropriate conclusions Pain DOI: 10.1016/j.pain.2009.07.036