Interleukin levels and depressive symptoms in psoriatic arthritis patients: insights from a case–control study on socio-demographic factors and disease perception

In the course of psoriatic arthritis (PsA), depression occurs much more often than in the general population. Depression can be considered a poor prognostic factor. The aim of the study was to assess the relationships between the occurrence of depression and the levels of proinflammatory cytokines in patients with PsA. The study included 86 (47F/39M) patients with PsA. Only patients with high disease activity (DAPSA > 28) were enrolled in the study. The severity of depressive symptoms was assessed using the Beck Depression Inventory II (BDI-II) for all patients. Additionally, sociodemographic data were collected. All patients were also assessed for the levels of interleukins (IL): IL-1, IL-6, IL-17A, IL-23, and tumor necrosis factor alpha (TNF-α) using the enzyme-linked immunosorbent assay (ELISA) test. In the study group, depression (BDI-II ≥ 14) was diagnosed in 45 patients (52%). Patients with coexisting depression reported higher levels of pain and disease activity on the visual analogue scale compared to patients without depression (8.5 vs. 7.7, p < 0.001 and 9.3 vs. 8.4, p < 0.001, respectively). The mean levels of proinflammatory cytokines [pg/ml], IL-1 and IL-6, were also higher in the group of patients with depression (46.4 vs. 4.7, p < 0.001 and 10.5 vs. 4.9, p < 0.001, respectively). The coexistence of depression in the course of Psoriatic Arthritis (PsA) is associated with higher levels of IL-1 and IL-6. Depression has a negative impact on the perception of the underlying disease and is linked to reduced social and occupational activity.