An exciting study reported in the latest issue of Nature Neuroscience from the laboratory of Dr. Marwan Baliki at Northwestern University in Chicago casts light on the changes that occur in the brain when acute pain becomes chronic. The study strongly suggests that subjects’ emotional responses to acute pain play an important role in predicting these changes in the brain. Subjects who are more distressed about their acute pain not only tend to go on to develop chronic pain but their distress actually caused changes in the brain that were observed on brain scans. To my knowledge, this is the first time we have actual observations of the changes our attitude and feelings can cause in the brain over time that can lead to the development of a chronic pain problem.
Dr. Baliki and his colleagues took brain scans of subjects with acute back pain. They also measured pain intensity and the level of distress the subjects were experiencing. These data were obtained 4 times over the course of one year. During this time, some subjects experienced a resolution of their back pain whereas others continued to experience significant back pain which by the one year mark, had become chronic.
Dr. Baliki and his colleagues found that the brain scans of the subjects with chronic pain showed differences that had emerged over the course of the year and that differentiated them from those subjects whose pain had resolved. They found that two areas of the brain that involve motivational and emotional responses, the nucleus accumbens and the medial prefrontal cortex, became more highly connected over time in the subjects whose pain became chronic. They also found that these subjects’ brains showed a decrease in the density of gray matter in the sensorimotor areas and in the nucleus accumbens over the course of the year, which indicates some degree of brain atrophy.
These findings are important because they indicate that changes in the brain that have to do with motivation and emotional response to pain predict which people with the same acute pain go on to develop chronic pain and which recover. In other words, if we only know the extent of a person’s injury or the degree of acute pain they are suffering, we cannot accurately predict who will go on to develop chronic pain. We need to know the person’s emotional reaction to the acute pain in order to make that prediction more accurately.
These data confirm the importance of psychological techniques for pain management which aim to help people cope more effectively and decrease distress and suffering. When people with acute pain decrease their distress and cope more adaptively, the study suggests that they are likely to prevent chronicity as well as the correlating negative brain changes.
Corticostriatal functional connectivity predicts transition to chronic back pain. Baliki, M.N., Petre, B., Torbey, S., Herrmann, K.M., Huang,L, Schnitzer, T.J., Fields, H.L., Apkarian, A.V. Nature Neuroscience, 15, 2012, 117-119.