More than seventy-five percent of people diagnosed with chronic depression also have recurring or chronic pain Conversely, thirty to sixty percent of people with chronic pain report symptoms of depression, according to the Archives of General Psychiatry.
To better understand the connections between pain and depression, Irina Strigo of the University of California San Diego and her colleagues studied brain images of people with chronic depression and discovered clues that help explain why so many of these same people also live with chronic pain.
Volunteers were told eight seconds beforehand that a painful experience was coming — being touched on the arm with a device hot enough to cause brief pain but not injury.
Strigo’s team tested 15 people in their mid-20s who were diagnosed with major depression, but not taking medication to treat it. Their magnetic resonance imaging ( MRI ) brain scans were compared to those of 15 similar people who did not have depression.
While anticipating the pain, the people with depression registered significantly more activity in the portions of the brain that process emotions, including the amygdala and insula, compared with the people with no depression.
The amygdala controls autonomic responses associated with fear, arousal, emotionas, and hormonal secretions, and has long been linked with a person’s mental and emotional state. This is where the “fight or flight” response originates, as well as directions to secrete stress hormones like cortisol and adrenaline.
The insula seems to direct what it “feels like to be human.” It’s the source of social emotions like lust, disgust, pride, humiliation, guilt and atonement. It’s believed to be the anatomical locus of moral intuition, empathy and the capacity to respond emotionally to music and other stimuli.
During the five seconds their arm was touched with the hot device, their brains continued to show increased emotional activity. During that same time, brain regions normally involved in managing pain were less active in the depressed people than the others.
“If a person has chronic pain together with depression, this is a very debilitating condition. This condition is very difficult to treat and the disability is much higher and the cost of treatment is very high,” Strigo said.
It is hoped that the study’s findings point toward new ways to help patients, either through behavioral therapies or medication.