Pain-related anxiety – more useful than catastrophising?

A couple of weeks back I summarised a few papers looking at the vexed term ‘catastrophising.’ Vexed, not because what is being measured isn’t a really useful construct (the risk of poorer outcomes across a whole raft of different painful conditions, from acute to long-term), but because the term carries baggage. The baggage is all that ‘exaggerated’ or ‘mountain out of a molehill’ weight that catastrophising has been associated with.

As an alternative, some authors have suggested we use the term ‘pain-related worrying’ – and I’m quite partial to the term ‘pain-related anxiety.’ Now the difference is subtle to some, but profound to others. Pain-related worrying is about what we do when anticipating the future in a way that leaves us feeling stressed – and often unable to stop unhelpful thinking. The theory goes that there’s a tussle between involuntary (bottom-up) attention grabbing information (threat), and voluntary (top-down) attentional control, with the presence of processing biases (based on previous experiences and threat value) and attempts to control or resolve the threat that result in being stuck worrying and feeling dreadful (my apologies to Hirsch & Mathews, 2012 for this very brief description!).

Pain-related worrying is about the thinking part. Pain-related anxiety is a slightly broader concept consisting of four aspect: cognitive, emotional, and physiological components of pain anxiety, as well as engagement in escape and avoidance behaviour (Vowles, et al., 2023, p. 177). One reason I like this concept is that it incorporates thinking, feeling, body responses and the efforts we take to avoid or control being in this state. This of course leads me to considering ACT approaches to help people become more willing to experience difficult stuff instead of avoiding or controlling.

One of my favourite measures of pain-related anxiety has been the PASS-20, a 20-item questionnaire that’s been around since 2002, based on the original developed in 1992. I liked using it clinically because items and scores on the subscales help guide where to put therapeutic energy: if the person can’t disengage from thinking, help them with that; if they’re afraid, help with that; if it’s about physiological arousal we can do something about that; and of course, we can help people begin to approach or go towards things they’re avoiding. For some reason the PCS grabbed attention more than the PASS-20, but it has been one of my go-to measures for decades and I do prefer it to the PCS.

Anyway. Today’s post is about a new and even more improved version of the PASS-20 and one that reduces the burden on people completing it while still offering robust psychometric properties. It’s the PASS-4 – wait? What?!! FOUR ITEMS! Yep, sure is.

How did they get to this? Well it’s all about item response theory. At this point in my post I want to openly admit my dyscalculia (a specific and persistent difficulty in understanding numbers which can lead to a diverse range of difficulties with mathematics) – I get the conceptual ideas, but my arithmetic is dire. Nevertheless, item response theory, which plays with statistics, identifies the items in a test that most accurately ‘fit’ the latent or hidden variable the questionnaire is trying to identify. It does this by estimating the probability of an identified response (eg certain items in a list) based on the interaction of a person’s latent ability and characteristics (eg difficulty and discrimination) of an item. The how it does this I leave to experts, but in plain language, items that few people respond to – but those that do score higher on everything else – are probably measuring something that only those with really high levels of anxiety (for example) would have. By sorting through the probabilities, the items that really do cut to the chase can be selected and used to work out who is in (ie is worrying) and who is not.

The items identified using this approach, from a pretty big study of more than 2500 people, were:

*During painful episodes it is difficult for me to think of anything besides the pain – cognitive
I find it hard to concentrate when I hurt – cognitive

*I avoid important activities when I hurt – escape/avoid
I will stop any activity as soon as I sense pain coming on – escape/avoid

*Pain sensations are terrifying – fear
When I feel pain, I am afraid that something terrible will happen – fear

*I find it difficult to calm my body down after periods of pain – physiologic

Pain seems to cause my heart to pound or race – physiologic

And if you only wanted to use four, pick the ones with the asterisk.

Now, why would you want to reduce the number of items? Well if you’ve ever had to complete a batch of questionnaires for research or clinical practice, you’ll know there are a heap to fill in. And we get bored… or don’t read the items clearly, or just want it to be over… so the longer a questionnaire is, the more risk we have in not doing a good job of completing it. The longer versions might offer more details – but at the risk of just not being done. So shorter is better. For some things.

For me – if I want to track a person’s progress repeatedly over the course of a six week programme, where I want to see if something I’m doing in the therapy sessions is having an impact, I’d like a brief set of items the person can quickly complete on their phone. And I’m a fan of repeated intensive measurements because they come closer to ‘daily life’ than the pre-treatment, post-programme and follow-up approach that is often used in RCTs. If I can track progress this quickly, I’m able to switch things up with my clinical interventions. This might mean people get back to their own lives without needing to see me, and that’s got to be a good thing.

Note well, though people: the authors point out that this study was conducted in a WEIRD group – white, educated, industrialised, rich and democratic – so needs further validation in other populations. They point out that the 4-item version is probably better than the 8-item, but that because it wasn’t studied longitudinally, that piece of work will need to be done.
Read the paper for more details – as always – and always consider whether self-report is the best way of measuring what’s changing when we’re working clinically.

Intrigued by intensive daily measures? – Read Mehl & Conner, Handbook of Research Methods of Studying Daily Life (Guilford, 2012).

Hirsch, C. R., & Mathews, A. (2012). A cognitive model of pathological worry. Behav Res Ther, 50(10), 636-646. https://doi.org/10.1016/j.brat.2012.06.007

McCracken LM, Dhingra L: A short version of the Pain Anxiety Symptoms Scale (PASS-20): Preliminary development and validity. Pain Res Manag 7:45-50, 2002.

McCracken LM, Zayfert C, Gross RT: The Pain Anxiety Symptoms Scale: Development and validation of a scale to measure fear of pain. Pain 50:67-73, 1992.

Vowles, K. E., Kruger, E. S., Bailey, R. W., Ashworth, J., Hickman, J., Sowden, G., & McCracken, L. M. (2024). The Pain Anxiety Symptom Scale: Initial Development and Evaluation of 4 and 8 Item Short Forms. J Pain, 25(1), 176-186. https://doi.org/10.1016/j.jpain.2023.08.001