While it makes sense intuitively that with an increase in depression you find a drop in physical performance, the mechanics of such a relationship merited investigation.
A new multicenter study has done just that.
The work, “Pain severity as a mediator of the association between depressive symptoms and physical performance in knee osteoarthritis,” appears in the August 6, 2018 edition of Osteoarthritis and Cartilage.
Alan Rathbun, Ph.D. research associate at the University of Maryland School of Medicine and co-author explained, “The motivation for the research described in the manuscript was based on prior studies of depression in osteoarthritis patients. Previous studies have provided strong evidence for interactive and nonlinear effects regarding depressive symptoms and its symptomatic consequences concerning pain and functional limitations in patients with musculoskeletal disorders.”
The authors wrote, “Three years of annual data from participants (n=1,463) with radiographic knee OA [osteoarthritis] in the Osteoarthritis Initiative (OAI) were analyzed. Depressive symptoms were measured using the Center for Epidemiological Studies Depression (CES-D) scale. Pain severity was evaluated with the Western Ontario and McMaster Universities Arthritis Index….”
“There are two important insights revealed by study findings,” Dr. Rathbun told OTW. “First, the results implied that in persons with radiographic knee osteoarthritis, depressive symptoms were associated with worse physical performance, but the proportion of the association mediated by knee pain severity (i.e., indirect effects) was never greater than 25%; and thus, the larger direct effects of depressive symptoms on physical performance indicate there is a large influence from the physical activity component of depression (i.e., apathy and inertia) or alternative mediators of this relationship.”
“Second, the direct effect of depressive symptoms on physical performance and indirect effects mediated by knee pain severity in persons with radiographic knee osteoarthritis follow the law of diminishing returns, where each unit higher of depressive symptom severity yields an incrementally lower per-unit direct and indirect effect on physical performance. More specifically, incremental differences in depressive symptom severity have a larger impact on physical performance at lower symptomology levels, but individuals with more severe depressive symptoms still have greater cumulative functional impairment than those with fewer symptoms of depression.”
“The ‘diminishing returns’ associated with depressive symptoms and its relationship to knee pain severity and physical performance in persons with radiographic knee OA may explain why unimodal treatment strategies (e.g., analgesics) with a single disease target are often less effective in those patients with comorbid depressive disorder.”
“Moreover, among OA patients receiving depression treatment who have more severe depressive symptoms, a larger improvement is needed to achieve the same intervention effect on OA disease severity as compared to smaller declines in those with lower depression severity. Conversely, the benefits of depression treatment on OA disease severity in these patients would increase exponentially with intervention efficacy.”
“Thus, treatments affecting depressive symptoms and OA disease severity simultaneously may be more efficacious than treatments with a single disease target, and likewise, combined treatment strategies using two interventions in parallel could be more effective than individual therapies alone.”
