For many, the impact of chronic pain may not be limited to the pain itself; it could also negatively affect their mental state.
New research by scientists at Northwestern University in Chicago may explain why people who have chronic pain also suffer from seemingly unrelated problems such as depression, anxiety, lack of sleep and trouble focusing.
"The pain is in your head," said Dr. Dante Chialvo, lead author of the study and associate research professor of physiology at the Feinberg School of Medicine. "The whole head."
The study showed that people with chronic pain have a portion of the brain that is always active: the region associated with mood and attention. This constant activity rewires nerve connections in the brain and leaves chronic pain sufferers at greater risk for mental problems.
Chialvo said that a healthy brain exists in a state of equilibrium, with about the same number of regions turned on and off. As certain regions are recruited for various tasks, other regions turn off to maintain the equilibrium.
But a person in chronic pain is not so even-keeled.
"We knew there are important differences in behavior in [chronic pain] patients," Chialvo said. "That has to come from brain abnormalities."
Chialvo described chronic pain as an idea that gets stuck in your head. The brain may not be able to attend to other tasks as well or as quickly because it is preoccupied with the pain signals.
Chialvo suggested that receiving pain signals constantly can result in mental rewiring that negatively affects the brain, and in particular, the regions associated with attention and mood. The rewiring forces their brains to allocate mental resources differently to cope with everyday tasks — from mathematics, to recalling a shopping list, to feeling happy.
The pain-brain connection has been well documented, at least anecdotally, and many doctors say they have seen firsthand how a patient's mental state can go downhill when they suffer chronic pain.
"Disordered sleep, less mental focus, mood irritability, and even depression with less overall joy and enthusiasm for life are what I see in this patient population," Dr. Doris Cope, professor and vice chairman of pain medicine at the University of Pittsburgh Medical Center's Pain Medicine Program.
Such may be the case with John Cannon, 70, who has had chronic low back pain for 40 years and says it takes him quite a while to fall asleep.
"There are nights that are better than others," he said. "It will take me a while to get into a comfortable position to go to sleep. … I just learned to operate differently."
Cannon, who is a participant in Chialvo's study, said he tries to not let the pain affect his life drastically, but in some situations, he wishes it weren't there.
"I do most things that I always do but I do them more slowly. … I know I'm going to pay the price if I lift [heavy things]. You get over those things, and I have."
Misconceptions about the pain-brain connection may have arisen from a lack of evidence that pain has a measurable, lasting impact on the brain.
But Chialvo believes his research finally quantifies the connection. His group's experiment monitored patients' brains while they tracked a moving object on a computer screen, a task that required minimal attention. Chialvo and his group found that patients with chronic pain had 50 times as many active regions in their brains than their pain-free counterparts.