The Role of Depression in Chronic Musculoskeletal Pain

It has been established that depression is more common in people suffering from chronic illness than in the general population (1,2). The epidemiologic relationship between pain and depression has been further studied in subpopulations, such as gender groups, the elderly, and in patients with heart disease (3–5). Unfortunately, that is about the point where the data stop and the extensively reviewed opinions begin (6). The problem is that there is no apparent mechanistic [i.e., cause and effect] relationship between depression and chronic pain (6). It is still far from clear that “depression, by itself, hurts”. In a study of patients with fibromyalgia syndrome [FMS], there were clear correlative relationships between the different pain/function measures studied and between the different psychological measures studied, but no cross-correlative relationship between the pain measures and the psychological measures (7). If the pain is the cause of the depression or if the depression worsens the perception of the pain, there should be a cross-correlative relationship between the severity of these two symptom domains. It should also be possible to treat the pain and see the depression improve or vice versa. That did not happen when effective analgesics for central sensitization-related pain [but lacking antidepressant activity] were used to treat patients with FMS (8,9). Depression emerged or persisted unchanged despite significant relief of the chronic pain. It is clear that more information is needed to mechanistically characterize what is commonly believed to be a relationship between depression and chronic musculoskeletal pain.

The first research contribution in this issue of the Journal of Musculoskeletal Pain [JMP] comes from Indianapolis, Indiana, United States (10). It was favored in this issue because it was a blinded, cohort-controlled, clinical trial with a substantial sample size. The authors pointed out that both musculoskeletal pain and depression are common clinical problems in society and that they separately account for a large portion of outpatient clinical care costs. They asked whether the course of musculoskeletal pain over one year would be altered by the presence of depression. In their study, they evaluated 150 patients with chronic musculoskeletal pain and comorbid depression [Group 1] in comparison to a second group of 250 patients with chronic musculoskeletal pain but lacking comorbid depression [Group 2]. It can be stated without equivocation that the two groups were remarkably similar at baseline with respect to demographic variables. So, why is not everyone with chronic pain also depressed? Why is chronic pain not a consistent comorbid complication of major depression? The reader will want to read the article to learn how patients in these two groups fared comparatively after 3 and 12 months of follow-up. What became of the depression in Group 1? and did the pain change differently in the two groups?

The second research contribution to this issue comes from Toronto, Ontario, Canada (11). These authors proposed to investigate the relationships between physical impairment, self-reported disability, and fear of neck movement in patients with chronic neck pain. They used a cross-sectional cohort study design to systematically evaluate a convenience sample of 35 middle-aged men and women whose main clinical complaint was neck pain for a duration of nearly five years. The reader is referred to the author's manuscript to see how these domain measures related to each other, how the authors interpreted their results, and what their data suggest as an approach to breaking the chronicity of this common pain problem.

From Tehran, Iran has come a report regarding postural control of women with chronic neck pain (12). The objective of the study was to evaluate the role of posture on pain due to myofascial pain syndrome [MPS] involving muscles of the neck. Measurements were accomplished with study subjects standing on a firm floor surface and separately while they were standing on a foam surface. Twenty-one women were evaluated and compared with an equal number of age- and gender-matched healthy normal controls. The results may countermand a natural preference of women for a soft surface on which to stand while accomplishing prolonged tasks like washing dishes or folding clothes.

A study reported from Vancouver, British Columbia, Canada evaluated the efficacy of a mechanical vibratory intervention on impairment and symptoms in patients with neck pain (13). The study was accomplished using a randomized, single-blinded, sham intervention-controlled design. It involved 44 men and women who had experienced neck pain for at least six months. The active intervention was considered to be more successful than the sham intervention, so the reader will want to compare magnitudes of change in each group and potential risks associated with the active intervention.

Investigators from Poznan, Poland have reported their experience with active interventions of laser or ultrasound therapy for each apparent MPS trigger point in the treatment region, as a proposed cause of the tennis elbow [lateral epicondylitis] symptoms (14). Their control groups received very low [theoretically ineffective or homeopathic] levels of the laser or ultrasound interventions. Their study design was a randomized, double-blind, double sham-controlled trial involving 80 patients, but that meant that there were only 20 patients in each treatment group. One way of thinking about this report would be as two parallel, sham-controlled trials of different active interventions. A possible way to enhance the statistical outcomes, if both active interventions are expected to be effective, might be to combine the active intervention groups and then compare them with the combined sham groups seeking a statistically significant effect of active intervention. The reader will want to determine whether the authors' conclusions are sufficiently well supported by the data to indicate using one or the other of the active interventions evaluated in this study.

Finally, a report from Seoul, Republic of Korea presents systematic measurements of anatomic changes in the tarsal tunnel depth with weight-bearing (15). Recall that the tarsal tunnel syndrome is a compressive neuropathy which occurs when the tibial nerve is traumatized as it accompanies the posterior tibial artery and three tendons through the tarsal tunnel behind the medial malleolus at the level of the ankle. The study population included healthy men and women of nearly ideal weight whose tarsal tunnel anatomy was examined ultrasonographically at supine rest and again with standing, weight-bearing. The objective was to identify structural changes that can occur with weight-bearing and might impact on the amount of space needed by the tibial nerve which occupies the central portion of the tunnel between the bone and the ligament. This report provides a review of the anatomy of the tarsal tunnel area of the foot and helps to define the clinical setting for the tarsal tunnel syndrome. Of course, this same technology could be applied by this same investigative team to situations [Ehlers–Danlos hypermobility, obesity, long narrow foot, lack of arch support, extensive barefoot walking, etc.] in which the tarsal tunnel syndrome might be expected to present with increased frequency.

An interesting case report of post-herpetic neuralgia comes from Sakarya and Ordu, Republic of Turkey (16). In their clinical description, the authors presented the course of a fairly young female patient whose sacral area involvement was complicated by intractable pruritus. The symptoms eventually responded to treatment. Readers are encouraged to learn from the unusual features of this case.

Please note the special interest columns provide reviews of papers in other medical journals since the previous issue of the JMP. The topics of these reviews are FMS, MPS, and other soft tissue pain syndromes.

As always, readers of the JMP are invited to submit original manuscripts for blinded peer review, case reports of general interest, research ideas to promote further investigation, and letters to keep us all informed. The JMP editorial office frequently receives relevant books to be evaluated by and for the benefit of our readers. Book reviewers are allowed to keep the featured book after the evaluation report is completed. Readers who would be interested in being a book reviewer for the JMP are encouraged to communicate that information to the editor.

Potential authors of contributions to the JMP should note that submissions and all communications between the authors and the JMP staff are to be accomplished online. For more details, visit http://mc.manuscriptcentral.com/wjmp.

The clear mandate of the International MYOPAIN Society [IMS], for which the JMP is the official journal, is to perpetuate the international meeting that is currently held every three years, but moving soon to an every two-year schedule. The next international meeting will be MYOPAIN 2013 and will be held in Seattle, Washington, United States. Two years later, the international MYOPAIN 2015 meeting will be held in Australia as the IMS responds to a plan to better serve our Asian members. The IMS website www.myopain.com will offer details as they become available.

Regional IMS Chapters are forming. It appears that the first Regional IMS Chapter to be officially organized will be in Thailand. Congratulations to them. We expect that one of the organizers will provide JMP readers with a Letter to the Editor describing the proceedings.