Depressive Symptoms Mediate the Relationship Between 25-Hydroxy Vitamin D and Self-Reported Pain Intensity in a Sample of Individuals Living with Non-Specific Chronic Low Back Pain

Purpose of the study Chronic Low Back Pain (cLBP) is one of the most prevalent musculoskeletal disorders in America, as well as the single leading cause of disability worldwide. Further, the overwhelming majority, approximately 90%, of cLBP is “non-specific” and is not attributable to any distinguishable pathology associated with the anatomical structures positioned between the posterior margin of the ribcage and the gluteal fold (low back). A growing body of literature suggests that psychobiological factors may contribute to cLBP severity. Existing research has shown that low concentrations of circulating 25-hydroxyvitamin D (Vitamin D) can not only exacerbate depressive symptoms but also has been linked to negative health outcomes, such as increased pain severity across musculoskeletal conditions. The aim of this pilot study was to investigate the extent to which depressive symptoms mediated the relationship between circulating levels of Vitamin D and self-reported pain severity in a sample of individuals living with cLBP. All research participants (N=93) completed The Center for Epidemiological Studies-Depression Scale (CESD) along with the Brief Pain Inventory- Short Form. Specimen samples were collected as part of a single blood draw to assay serum levels of circulating Vitamin D. Depressive symptoms significantly mediated the association between circulating levels of Vitamin D and self-reported pain severity as indicated by scores on the BPF-SF [Indirect Effect = -.8931, 95% CI: -2.1433 to -.0640]. As hypothesized, lower levels of circulating Vitamin D was significantly associated with greater depressive symptoms (p < .001), which was sequentially associated with greater pain severity (p = .003). Our findings suggest that Vitamin D deficiency and depression may be risk factors that contribute to greater pain severity. Furthermore, symptoms related to depression might be an underlying mechanism through which Vitamin D influences cLBP severity. NIH/NIMHD #R01MD010441.