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Crossing your fingers may help reduce pain

11:00am Friday 27th March 2015 content supplied byNHS Choices

"Crossing your fingers might reduce pain," says The Guardian. The study behind the news found crossing your fingers may confuse the way your brain processes feelings of hot and cold - and, in some cases, reduce painful sensations.

Rather than subjecting the participants to "normal" pain, the authors used a trick known as the thermal grill illusion. The thermal grill illusion is not the latest in BBQ technology, but an unusual - and well validated - phantom pain effect.

When the skin is subjected to an alternating pattern of harmless coldness followed by heat, it creates a sensation of "burning coldness", but does no damage to the skin. It is something akin to the burning sensation felt by anyone placing cold hands under warm water after a snowball fight.

The researchers applied hot and cold sensations to the ring, middle and index fingers to create phantom pain sensations in volunteers. The phantom pain reduced in some people when they crossed their fingers.

This artificial phantom set-up means the findings probably don't apply to most real-life experiences of pain. Would a woman crossing her fingers during childbirth feel some benefit, or would someone who has just hit their thumb with a hammer? Probably not.

We shouldn't get too hung up on the crossed finger idea, though. The concept behind it is more interesting. The study tentatively showed that pain might be influenced by how our bodies are organised in space and relative inputs from different parts of your body.

If it is found to be a regular and real occurrence through more research, this may have potential for use in pain management in healthcare.

Where did the story come from?

The study was carried out by researchers from University College London (UCL) and the University of Verona (Italy).

It was funded by the CooperInt Program from the University of Verona, the European Union Seventh Framework Programme, the Economic and Social Research Council, and the European Research Council.

The study was published in the peer-reviewed science journal Current Biology.

The Guardian reported the story accurately, making it clear it was not real-world pain, but phantom pain from the thermal grill illusion.

The paper interviewed Elisa Ferrè of UCL and a co-author, who said: "There might be applications for treating people with chronic pain . the position of your limbs or digits is something that would be very easy to manipulate."

Adding a welcome note of caution, The Guardian wrote: "The findings did not establish whether crossing your fingers would be as soothing with a real painful stimulus, rather than an illusory one, but Ferrè said her hunch is that it would help."

What kind of research was this?

This was a study of human volunteers investigating whether pain perception is influenced by the position of their fingers.

Rather than subjecting the participants to conventional pain, the team used a trick known as the thermal grill illusion to create a phantom pain sensation.

Controlled experiments such as these are useful for developing new ideas and testing them in the early stages. But testing pain in an indirect manner like this isn't ideal. It would be more useful to devise a test using actual pain, but this has ethical dimensions to consider.

What did the research involve?

The researchers used three heat pads under the index, middle and ring fingers of participants to test different combinations of the thermal grill illusion, and whether crossing fingers reduced the phantom pain.

Participants also adjusted a temperature delivered to the other hand until it matched their perception of the cold target finger (index or middle).

The thermal grill illusion works by applying a warm sensation to the index and ring fingers, and a cold sensation to the middle finger. The grill-like pattern of warm-cold-warm creates a burning sensation in the middle finger, even though it is in fact exposed to cold.

About half of people go as far as describing the feeling as painful. The sensation is much more intense than the hot or cold on their own.

According to the researchers, the illusion might work because the hot sensation in the outer two fingers blocks the activity in a certain cooling receptor under the skin. With this pathway blocked, the hot signals from the nearby hot areas are felt more intensely.

What were the basic results?

The study found significant temperature overestimation when the target finger was in the middle (warm-cold-warm) compared with on the end (cold-warm-warm).

The effect depended on the target finger being in the middle of thermal inputs, but it didn't matter whether this was the index or middle target fingers.

The thermal grill effect for the middle finger was abolished when it was crossed over the index. The same effect was generated for the index finger when it was crossed with the middle.

How did the researchers interpret the results?

The team concluded that, "Our results suggest that the locations of multiple stimuli are remapped into external space as a group; nociceptively mediated sensations [pain perception] depended not on the body posture, but rather on the external spatial configuration formed by the pattern of thermal stimuli in each posture."

Conclusion

This study investigated pain using a thermal grill trick, which applies hot and cold in different combinations to the index, middle and ring fingers to induce a phantom burning sensation.

This showed that crossing your fingers may confuse the way your brain processes feelings of hot and cold, and in some cases stopped the phantom pain.

The biggest limitation of this study is that it looked at phantom pain using the thermal grill trick, rather than actual pain. Phantom pain may be different from "normal" pain, so the results may not relate to a regular pain situation.

We shouldn't get too hung up on the crossed finger idea, though. The concept behind it is more interesting. The study tentatively showed that pain might be influenced by how our bodies are organised in space, and relative inputs from different parts of your body.

If found to be a regular and real occurrence through more research, this may have potential for use in pain management in healthcare.

For example, The Guardian says: "Scientists believe the phenomenon could ultimately be harnessed to help treat chronic pain patients, who suffer from painful sensations, often long after a physical injury has healed."

At present, this is largely speculative. The study only showed reduction in phantom pain, and only under a very specific and artificial set of circumstances. Research that is more relevant and applicable to real life would be the logical next step for this research field. 

Still, how we think about pain can sometimes alter how it much it affects us. Many people find cognitive behavioural therapy (CBT) techniques can be useful in helping people cope better with chronic pain.

Read more about coping with pain.

Analysis by Bazian. Edited by NHS Choices. Follow Behind the Headlines on Twitter. Join the Healthy Evidence forum.

Summary

"Crossing your fingers might reduce pain," says The Guardian. The study behind the news found crossing your fingers may confuse the way your brain processes feelings of hot and cold.

Links to Headlines

Crossing your fingers might reduce pain, says study. The Guardian, March 26 2015

Crossing your fingers actually DOES help - just not the way you expect. Metro, March 26 2015

Links to Science

Marotta A, Ferrè ER, Haggard P. Transforming the Thermal Grill Effect by Crossing the Fingers. Current Biology. Published online March 26 2015

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