Psoriatic Arthritis Risk Increased by Depression Among Patients With Psoriasis
Systemic inflammatory effects are present in psoriasis, PsA, and MDDs.
Researchers from Canada have demonstrated that depression is a significant risk factor for progression from psoriasis to psoriatic arthritis (PsA). Led by Ryan Lewinson, MD, PhD, from the Cumming School of Medicine at the University of Calgary, Alberta, Canada, the investigators found that patients with psoriasis who developed a subsequent major depressive disorder (MDD) significantly increased the risk of developing PsA by as much as 37%.1
Dr Lewinson and colleagues pointed out that systemic inflammatory effects are present in psoriasis, PsA, and MDDs and wanted to explore whether elevated inflammation as a result of the external stresses of an MDD would cause psoriasis to cross a threshold point that led to progression beyond skin disease into PsA.
"Our objective was to evaluate clinical data to elucidate the possible role of MDD in the progression of inflammatory disease from one organ system (the skin) to involving multiple organ systems, and thereby highlight a possible risk factor for PsA development among patients with psoriasis," the investigators wrote in a report published online February 22 in the Journal of Investigative Dermatology.
To evaluate their hypothesis, the investigators used The Health Improvement Network (THIN) medical records database in the United Kingdom. The general practice database yielded 73,447 individuals diagnosed with psoriasis who were followed up for a 25-year period, from 1987 to 2012.
The study was split into two cohorts: patients with psoriasis who developed an MDD (n = 5216) and patients with psoriasis who did not develop a subsequent MDD (n = 68,231). The investigators used Cox-proportional hazards models, and the subsequent analysis demonstrated a significant increase in risk of developing PsA among the MDD group compared with the non-MDD group (unadjusted hazard ratio [HR], 1.56; 95% CI, 1.28-1.90; P <.0001).
Dr Lewinson and colleagues also analyzed the data for potential confounding variables, and "alcohol use was the only covariate that was identified as having a potential confounding effect on the MDD and PsA association among patients with psoriasis," they observed. When adjusted for alcohol use, the investigators found that among patients with psoriasis, MDD remained a significant risk factor for developing PsA (HR, 1.41; 95% CI, 1.10-1.80, P =.007). When further adjusted for all covariates, the analysis yielded a conservative estimate of risk that remained statistically significant (HR, 1.37; 95% CI, 1.05-1.80; P =.021).
Summary and Clinical Applicability
"The present study has expanded our knowledge in this area by identifying a temporal relationship between psoriasis, MDD, and PsA and conservatively demonstrates that MDD increases the risk of developing PsA among patients with psoriasis," Dr Lewinson and colleagues wrote, reflecting on the study results. "As such," they added, "this study highlights important considerations for clinicians, who should exercise heightened awareness and primary prevention strategies for MDD among patients with psoriasis, as MDD appears to significantly increase the risk of developing PsA."
The investigators, however, pointed out that the results of this study only demonstrate the increased risk of developing PsA among patients with psoriasis who have an MDD. What it did not show, they reinforced, was a causal relationship between MDD and PsA, as patients with psoriasis developed PsA in the absence of any MDD, whereas not all patients with psoriasis and subsequent MDD progressed to PsA. "Thus, other risk factors remain to be discovered that also contribute to the development of PsA," they advised.
- The study design prohibited the investigators from evaluating all possible confounding or mediating variables and prevented them from creating a causal model of why MDD increases the risk for PsA.
- The association of MDD as a risk factor for PSA among patients with psoriasis may be explained, in part, by mediating variables that were not directly evaluated in this study.
- The study did not evaluate serum markers of systemic inflammation.
- Lewinson RT, Vallerand IA, Lowerison MW, et al. Depression is associated with an increased risk of psoriatic arthritis among patients with psoriasis: a population-based study [published online February 22, 2017]. J Invest Dermatol. doi:10.1016/j.jid.2016.11.032