Why can stress and fear block pain?

THAT'S THE WHY:Have you ever wondered why, in high-stress situations, sometimes people can just keep going through the pain barrier?

From athletes who get up and complete a race or match after an injury, to soldiers who manage to carry on even though they are wounded; it’s an extraordinary feat of the human body.

Why can immediate stress or fear block pain? Dr David Finn and colleagues at NUI Galway have been studying such “stress-induced analgesia”, and in particular how pain can be blocked during exposure to learned psychological stress or fear.

They have been looking at how the brain’s own drug-like opioid and cannabinoid chemicals appear to drive this phenomenon.

In a recent paper in the journal Pain, they describe how increasing the levels of a particular endocannabinoid (a marijuana-like chemical produced by the body) can suppress pain during fear.

And in their experimental model, researcher Dr Gemma Ford found a region of the brain called the hippocampus was an important site of action in blocking this pain.

“The hippocampus is a brain region more commonly associated with memory, but here we have shown that it also has an important role to play in the potent suppression of pain by fear,” says Finn, whose work was funded by Science Foundation Ireland.

“This is a very potent type of pain suppression and if we could understand the biological factors involved in driving it, then we may be able to harness that knowledge to identify new therapeutic targets for the treatment of pain and stress-related disorders.”