Study Links Depression and Pain
Pain Severity Predicts Treatment Outcome
By Salynn Boyles
WebMD Medical News Reviewed By Brunilda Nazario, MD
on Thursday, August 26, 2004
Aug 26, 2004 -- Physical pain is a common, but often ignored, symptom of depression; and pain severity is a strong predictor of the degree of depression and health-related quality of life, findings from a newly published study indicate.
Two-thirds of the depressed patients beginning antidepressant treatment in the study reported being in physical pain, with the most commonly cited symptoms being frequent headaches, back pain, joint pain, and abdominal pain.
Physical symptoms persisted longer than depression symptoms in more than a third of the patients, leading the researchers to conclude that pain may serve as a barometer for gauging the effectiveness of depression treatment. The findings are reported in the August issue of the journal Psychosomatic Medicine.
"It is important to recognize that physical symptoms like pain can be part of the picture of depression," researcher Kurt Kroenke, MD, tells WebMD. "Even though the physical symptoms may be related to or aggravated by the depression, they can linger longer than the emotional symptoms."
Pain Masks Depression
The study included 573 clinically depressed patients being treated at one of 37 clinics. Roughly four out of five patients were women, a similar percentage was white, and all were being started on a selective serotonin reuptake inhibitor (SSRI) antidepressant, such as Paxil, Zoloft, or Prozac.
Over the next nine months, the researchers measured the rates of physical symptoms in depressed patients as well as their impact on quality of life and depression treatment.
At three months, patients who reported being in severe pain were four times as likely as those who did not report pain to have a poor response to antidepressant treatment, and those who reported being in moderate pain were twice as likely to have a poor response.
Kroenke and researcher Matthew J. Bair, MD, note that the common co-occurrence of depression and pain symptoms may explain why depression is often unrecognized in the primary care setting.
"The [physical] symptoms often predominate and may distract attention from comorbid depressive symptoms," they write. "The new emphasis on pain as the 'fifth vital sign' … provides an opportunity for better recognizing and understanding the interaction between depression and pain."
Common Chemical Pathways
Recent research has shed some light on the link between depression and pain, showing that the two share common chemical pathways, Kroenke says. Just as the brain chemicals, serotonin and nor-epinephrine are known to play key roles in depression, the neurotransmitters are now believed to also mediate pain.
Thomas J. Beckman, MD, of the Mayo Clinic, tells WebMD that doctors are increasingly aware of the link between depression and pain, but convincing patients that the two are related remains a challenge.
Beckman addressed the subject in a letter recently published in the Archives of Internal Medicine. He wrote that once a physical cause is eliminated after an evaluation, patients should be encouraged to focus on ways of treating the pain rather than finding its cause.
"I encourage the patient to embrace the notion that people commonly have unexplained symptoms and that the patient should attempt making a transition from seeking a cause to coping with the reality of having medically unexplained symptoms," he writes. "After patients consider their symptoms and depression in this context, a surprising number of them seem to understand and accept their depression-pain syndrome."
SOURCES: Bair, M. Psychosomatic Medicine, August 2004; vol. 66: pp 17-22. Kurt Kroenke, MD, professor of medicine, Indiana University; and research scientist, Regenstrief Institute, Indianapolis. Thomas J. Beckman, MD, consultant in internal medicine, Mayo Clinic; and assistant professor of medicine, Mayo Medical School, Rochester, Minn. Beckman, T. Archives of Internal Medicine, April 12, 2004; vol 164: pp 804-805.