Could manual therapy be the narcotic of pessimists?

I am an optimist but I am thinking about jumping the fence – joining the dark side of pessimism and excessive dread. Maybe I am being a bit hasty? I know we all think that there is little benefit in pessimism and that we would rather have an optimistic patient come in the door than a pessimistic one. There is an entire industry based on pop-psych methods to get us more optimistic. Optimism might even be something we should teach our kids (this one claims to be a proven safeguard against depression. Big claim.) and I can see the inherent value in it. But isn’t there some advantage to pessimism? It seems there might be and it seems I am just a little more interested in getting a few more pessimistic patients through the door.

The irrepressible people at Oxford University’s Centre for functional imaging of the brain have just done a study that strongly suggests that there might be at least one benefit in pessimism as it relates to pain. Now, first up, I should declare a massive conflict of interest on this – I worked at fMRIB and I hold four of the five authors in very high regard – not just as scientists but as very high quality people. It is not that the fifth author is a dud – I just don’t know him. While we are on fMRIB – they got their new whizz-bang 7T brain scanner earlier this year, which is a pretty major aquisition – it must have cost a small bomb just putting the thing in – here are a few slides of how it was done.

Back to the experiment. 18 healthy volunteers completed a simple measure of pessimism/optimism and then did two tasks while they were in the fMRI scanner. The first task involved showing the participants a warning cue on the screen. The warning cue said something like ‘here it comes sucker’ and then about 10 seconds later, they either got a very painfully hot stimulus to their hand or they got a safety cue that said something like ‘just kidding’ (these are not the real cues – you can read about the real cues here).  A further 9 seconds later they were asked to rate the pleasantness of their relief at getting the ‘just kidding’ cue.

The second task was a general reward imagination task. It has been done before and involves written descriptions of scenarios that are either pleasant or neutral – there is actually a well used list called the SHAPS which has been shown to get you salivating and get your dopamine system going.

The key result from the fMRIB study was the BOLD response when the ‘just kidding’ cue was shown and its relationship to pessimism scores. A quick word on BOLD – BOLD stands for the blood oxygen level dependent response, and corresponds to where in the brain there is a statistically increased level of oxygenated haemoglobin (called an ‘overshoot’). This overshoot is thought to reflect the diversion of blood to active synapses. The results were, conveniently, just as the authors predicted – the nucleus accumbens and the ventral prefrontal cortex were the most obvious brain areas associated with the just kidding cue. The nucleus accumbens activation correlated nicely with optimism/pessimism scores. This is not altogether surprising I guess – this brain area has been implicated before in association with an unexpected reward or outcome.  That nucleus accumbens activation was differentially active between pessimists and optimists was obvious: in optimists, there was very little activation of this area and they reported very little relief at getting the ‘just kidding’ cue. To see how different nucleus accumbens activation was between optimists and pessimists, check out Figure 4 on the paper.

The second task revealed a wider activation associated with reward type scenarios. You can check out where if you want by looking at their nice pictures.

So, what does this study show? It shows what we might actually think is intuitively sensible – pessimistic people get more relief when pain is averted than optimistic people do and it is not that pessimists are lying about it – their brain imaging data corroborate their story.  I wonder if this implies that when a pessimistic person discovers that something is not as bad as they expected – for example discovering that a certain movement is not as painful as they predicted it would be – there will be a nice big juicy reward-type activation in the brain. Perhaps then, pessimistic people are more likely to become ‘addicted’ to manual therapy techniques that give them an immediate almost ‘magic’ pain relief. Could manual therapy be the narcotic of pessimists?  Indeed is it possible that a pessimist would do things they expect to be painful on the off chance they will not be and thus throw themselves into a nucleus accumbens-driven euphoria?  A touch speculative perhaps.

About Lorimer Moseley

Lorimer is NHMRC Senior Research Fellow with twenty years clinical experience working with people in pain. After spending some time as a Nuffield Medical Research Fellow at Oxford University he returned to Australia in 2009 to take up an NHMRC Senior Research Fellowship at Neuroscience Research Australia (NeuRA). In 2011, he was appointed Professor of Clinical Neurosciences & the Inaugural Chair in Physiotherapy at the University of South Australia, Adelaide. He runs the Body in Mind research groups. He is the only Clinical Scientist to have knocked over a water tank tower in Outback Australia.

Link to Lorimer’s published research here. Downloadable PDFs here.

Reference

ResearchBlogging.org

Leknes S, Lee M, Berna C, Andersson J, & Tracey I (2011). Relief as a reward: hedonic and neural responses to safety from pain. PloS one, 6 (4) PMID: 21490964