Treat chronic pain and depression independently

Allison Gandey

May 19, 2005

May 19, 2005

Ann Arbor, MI - While depression and pain frequently present in tandem, the two conditions are independent of each other, and researchers say this may explain why antidepressants with no analgesic properties have been ineffective in relieving pain. "There is an incorrect impression among many doctors that if you treat a patient's depression, it will make their pain better. Not so," senior author Dr Daniel Clauw (University of Michigan, Ann Arbor) said in a news release. "If someone has pain and depression, you have to treat both."



 
 
Dr Daniel Clauw (Source: University of Michigan Medical School)

 



In a study appearing in the May 2005 issue of Arthritis & Rheumatism, the researchers used functional magnetic resonance imaging of the brain to determine that in patients with fibromyalgia, their level of depression has little influence on the intensity of pain they experience [ 1 ]. "We have seen that if you give antidepressants to the average patient with fibromyalgia, they'll come back a couple of months later and say, 'My pain isn't any better, but I don't feel so sad about it,' " Clauw said. "Our research provides further evidence that these pathways are quite independent."

While other clinical research has supported the idea that pain and depression should be treated independently of each other, the researchers say this is the first time it has been shown using functional imaging brain scans.

There is an incorrect impression among many doctors that if you treat a patient's depression, it will make their pain better. Not so. If someone has pain and depression, you have to treat both.

Approximately 30% to 54% of people with chronic pain also have a major depressive disorder. The researchers, led by Dr Thorsten Giesecke (University of Michigan, Ann Arbor and University of Cologne, Germany), write that among the many hypotheses about depression and chronic pain are the notion that 1 causes the other or that a common underlying diathesis causes individuals to be more susceptible to both major depressive disorder and chronic pain.

Conducted at the Georgetown University Medical Center, the study involved 33 women and 20 men with fibromyalgia; in addition to these 53 patients, another 42 healthy control participants were included. The researchers measured the pain experienced by subjects based on their tolerance of pressure applied to their left thumbnails using a hard rubber probe. The investigators also conducted interviews and had the subjects fill out questionnaires. Using functional imaging scans, they compared the subjects' magnitude of pain, experimental pain sensitivity, and symptoms of depression.


Different sensory and affective elements to each individual's pain experience?

"In patients with fibromyalgia, neither the extent of depression nor the presence of comorbid major depression modulates the sensory-discriminative aspects of pain processing [such as] localizing pain and reporting its level of intensity," Giesecke and colleagues write. "However, depression is associated with the magnitude of neuronal activation in brain regions that process the affective-motivational dimension of pain. These data suggest that there are parallel, somewhat independent neural pain-processing networks for sensory and affective pain elements."

The researchers explain that while this study identified the mediating processes between symptoms of depression or major depressive disorder and pain and their anatomic correlates in the brain, the design could not determine the independent influence of either chronic pain or depression on each other. They note, "The ideal way to address the causality between chronic pain and depression in future studies is to evaluate patients with chronic pain as they transition between depressed and nondepressed states."

Giesecke and colleagues emphasize that chronic pain, major depressive disorder, and other forms of these conditions frequently coexist. "Although it is tempting to lump these constructs together because they can occur and may have common mechanisms, it may not be prudent to extrapolate this concept to individual patients. It appears as though there are different and easily distinguished sensory and affective elements to each individual's pain experience." They point out there are strong data suggesting that these elements are somewhat independent of each other and respond differentially to both pharmacologic and nonpharmacologic interventions. "Evaluation of these sensory and affective dimensions in patients with chronic pain is likely to improve diagnosis, choice of treatment, and treatment efficacy."

Source

  1. Giesecke T, Gracely RH, Williams DA, et al. The relationship between depression, clinical pain, and experimental pain in a chronic pain cohort. Arthritis Rheum 2005; 52:1577-1584. Abstract


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