Our results concur with previous studies about the prevalence of comorbid depression in RA; 37% of RA patients in our cohort meet criteria for moderate to severe depressive symptoms. As reported previously in the literature, increased HAQ scores and low SES are associated with depressive symptoms in patients with RA (21
). However, stratifying patients by outpatient clinic site reveals new and important findings.
Without regard to clinic site, there are increases in depression score for each unit increase in the HAQ. Receiving care at the public county clinic is also associated with higher increases in depression scores. However, when patients are stratified by clinic site (), the change in depression score becomes more meaningful. The tacit assumption that disability and SES have independent consequences on depressive symptoms in patients with RA does not hold. One potential explanation for our results is that at every level of functioning, persons from a lower SES may not have the support and coping skills to perform as well as those from a higher SES, leading to even higher rates of depression. Likely, there are different psychological effects with regard to functional limitations for the immigrant who seeks care at a public hospital clinic compared with the patient who gets treatment at a tertiary care clinic. For example, disability that causes a work disruption for individuals in manual labor jobs, as opposed to white collar, professional jobs, could lead to greater depressive symptom severity.
There are limitations to our study. The design was cross-sectional and therefore causality between greater HAQ scores and the associated, increased depressive symptoms cannot be established. However, a previously conducted longitudinal study (46
) showed that the temporal relationship between arthritis and mood disorders, such as depression, is unidirectional and that preexisting arthritis leading to disability elevates the risk of depression and not vice versa. Furthermore, it has also been shown that functional decline precedes the onset of depression (23
), so while causality cannot be proven in this study, it has been established with prior longitudinal data.
As in other chronic conditions, assessing depressive symptoms in patients with RA can be difficult. It is well understood that somatic symptoms of depression (e.g., fatigue or decreased energy) overlap with symptoms of RA. Consequently, there is a risk that depression in RA may be overestimated (47
). Another limitation is that patients seen at the county hospital may represent a sicker population then those referred to the tertiary care center rheumatology clinic. This is likely a reflection of referral practices to a public urban hospital clinic.
Our accessible population, i.e., urban, underserved patients as well as those seen at a university-affiliated clinic, may not be generalizable to all patients with RA. Using clinic site as a proxy for SES may also be a limitation related to generalizability since it reduces the ability for others to replicate results. However, by comparing well-validated measures of SES (race/ethnicity, education, income, health access, and immigrant status) in a subset of patients between the clinic sites, we attempted to measure as much relevant socioeconomic information as possible. By considering how clinic site may measure SES in a thoughtful way and acknowledging its limitations, we believe that it functions as a dependable proxy for SES in this sample.
Poor health outcomes persist in patients with RA and depression despite advances in available treatment. Recognizing the variability in psychological effects in patients with RA, such that a vulnerable population is at higher risk of depression, can help guide treatment to include prevention of functional limitations and subsequent depression in these susceptible patients. For example, patients who receive adequate emotional support report fewer depressive symptoms (48
). A treatment program that includes psychological support targeted toward patients with low SES may ameliorate health inequalities in this vulnerable population.
There are disparities in both physical and mental health among individuals with low SES, and the presence of poor physical functioning exacerbates the disparity in mental health. The interaction between functional limitation and low SES in patients with RA suggests that, for the same level of disability, patients with low SES may be more likely to experience depression. Failure to acknowledge this interaction may perpetuate health disparities by ignoring these differences. Detection and documentation of the differing effects of disability on depression between patients of different SES can help rheumatologists move forward to creating solutions and improving health outcomes by initiating treatment for depression.