CHRONIC BACK PAIN IMPAIRS DECISION MAKING
Scientific evidence supports the hypothesis that
chronic pain impairs an individual's decision-making capability
As part of one study, investigators compared 26
healthy people with 26 patients with chronic back
pain (CBP) and 12 patients with a condition called
chronic complex regional pain syndrome (CRPS).
CRPS is a chronic nerve disorder typically afflicting
the arms or legs, which usually onsets following an
The study participants were asked to perform a test researchers use to assess emotional decision-
making. The test, called the Iowa Gambling Task,
is a gambling card game.
Subjects with CBP performed 41% worse than did
pain-free individuals. Those with CRPS performed
The study's authors conclude that "our evidence indicates that chronic pain is associated with a specific cognitive deficit, which may impact every
day behavior especially in risky, emotionally laden, situations."
"Other cognitive abilities, such as attention, short-
term memory, and general intelligence tested
normal in the chronic pain patients."
Aching atophy: more than unpleasant, chronic pain shrinks the brain
An occasional headache is a nuisance, but severe, unrelenting pain can blight your existence. Often leading to anxiety and depression, chronic pain, scientists have learned, can shrink the brain and may impair one of the most valuable mental functions: the ability to make good decisions.
Pain is a defense system that indicates when something is wrong, explains Marshall Devor (Hebrew University of Jerusalem). "When there is a persistent tissue disorder or there has been injury to the nerves, it's like an alarm that is broken. Pain becomes a disease in its own right," Devor points out.
Pain signals originate at the site of injury but soon lay siege to the entire nervous system. When pain is unremitting, dramatic changes follow: spinal cord neurons become hypersensitive and start firing in response to weak stimuli. This hyperexcitability ratchets up all pain responses, which explains why people with diseases such as arthritis, cancer and diabetes, or with nerve trauma caused by surgery, sometimes experience widespread pain from even the lightest touch.
"Pain always travels to the brain," insists Vania Apkarian (Northwestern University) a bioelectrical engineer and physiologist, "and could cause damage". To test his hypothesis, Apkarian resorted to magnetic imaging. Zooming in on the brain chemical N-acetyl aspartate (the amount of which correlates with the density of neurons) he identified a striking difference in the prefrontal cortex. Pain was triggering brain atrophy there, apparently.
Apkarian compared the overall volume and regional grey matter density in patients who had chronic back pain with controls. The preliminary results were revealing: the average atrophy was greater in people with lower back pain than normal. "The difference is highly significant," he comments.
Because the prefrontal cortex is crucial for emotional decision-making, Apkarian wondered if constant pain might be clouding people's judgment. He asked 26 people who had suffered lower back pain for more than one year and 29 normal volunteers to play a gambling card game called the Iowa Gambling Task. The test was originally developed by neuroscientist Antonio R. Damasio (University of Iowa) and his colleagues to study decision-making in risky, emotionally laden situations. It involves selecting cards from decks with different potential cash payouts and penalties. Normal subjects learned to optimize their choices, but participants with a pain history made bad decisions, averaging 40 percent fewer good choices compared with normals. What's more, the amount of suffering correlated with how badly they played. "Chronic pain is driving these people to make poor judgments," concludes Apkarian.
Yet other cognitive abilities remained intact. "None of these patients are dramatically impaired," says Apkarian, who excluded from the study people with high depression or anxiety to avoid confounding factors. "This study raises the question of whether these people are making appropriate decisions in every day life," speculates. Apkarian, who found similar results with sufferers of chronic complex regional pain syndrome, a nerve disorder that may follow injury to the arms or legs.
"These are very interesting results, but we need to know more about what these changes really mean. Are they reflecting changes in brain metabolism or true nerve cell loss?" opines Anthony Jones (University of Manchester, UK), Director of the human pain research group. "It seems unlikely that a strong sensory input would cause brain damage since we know the brain is so good at protecting itself," he adds. If the loss is real, then the next step would be to determine if the damage can be reversed-and compensate for painful choices.
Dr Lisa Melton—Science Writer, Novartis Foundation, London