The brains of those with major depressive disorder appear to react more strongly when pain is anticipated and also show altered functioning of the neural network that modifies pain sensitivity, according to a new report.
Chronic pain and depression are common and often overlap each other, say study authors Irina A. Strigo and her colleagues at the University of California San Diego, LaJolla. Recurring or chronic pain occurs in 75% of patients with depression and between 30-60% of patients with chronic pain have depression. Understanding the relationship between depression and pain is important because of poorer outcomes and increased treatment costs when both are present.
The researchers studied 30 young adults, half who had major depressive disorder and were taking medication and half who did not have depression. All participants were given a questionnaire regarding their tendency to magnify, ruminate or feel helpless when faced with pain. They then underwent functional magnetic resonance imaging (MRI) while their arms were exposed to both a painful temperature and a non-painful temperature. A visual cue was also presented as the heat was applied (green for non-painful and red for painful).
The researchers found that the participants with depression, when compared with those who didn’t have depression, showed increased activation in certain areas of the brain when they anticipated a painful temperature. They also showed less activation in other areas, including those responsible for adjusting sensitivity to pain.
Another interesting finding was that those who had higher helplessness scores on the questionnaire had greater brain activity when they anticipated pain.
“The anticipatory brain response may indicate hypervigilance to impending threat, which may lead to increased helplessness and maladaptive modulation during the experience of heat pain,” say the authors. “This mechanism could in part explain the high comorbidity of pain and depression when these conditions become chronic.”
The study appears in the November issue of Archives of General Psychiatry.
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