"Emotions – or mood – can alter how we react to pain since they're interlinked," says lead author Mathieu Roy. "Our tests revealed when pain is perceived by our brain and how that pain can be amplified when combined with negative emotions."
The discovery provides scientific evidence that pain is governed by mood and builds on the authors' previous work which showed how pleasant music could decrease aches. "Our findings show that non-pharmaceutical interventions – mood enhancers such as photography or music – could be used in the healthcare to help alleviate pain. These interventions would be inexpensive and adaptable to several fields," says Roy.
As part of the study, 13 subjects were recruited to undergo small yet painful electric shocks, which caused knee-jerk reactions controlled by the spine that could be measured. During the fMRI process, subjects were shown a succession of images that were either pleasant (i.e. summer water-skiing), unpleasant (i.e. a vicious bear) or neutral (i.e. a book). Brain reaction was simultaneously measured in participants through functional magnetic resonance imaging (fMRI).
The fMRI readings allowed the scientists to divide emotion-related brain activity from pain-related reactions. "We found that seeing unpleasant pictures elicited stronger pain in subjects getting shocks than looking at pleasant pictures," says Roy.
Citation: Mathieu Roy, Piché, Mathieu, Chen, Jen-I, Isabelle Peretz, Pierre Rainville, 'Cerebral and spinal modulation of pain by emotions', PNAS, 2009