Psoriatic arthritis and depressive symptoms: does systemic inflammation play a role?

Depression is commonly associated with psoriatic arthritis (PsA), but its risk factors in these patients are largely unrecognized. Pro-inflammatory cytokines involved in the pathogenesis of PsA have been associated with depression in patients without autoimmune diseases. The aim of this study was to establish whether PsA patients with and without depressive symptoms differed for general or clinical variables and serum cytokines milieu.

One hundred and fifty consecutive patients with PsA were screened for depressive symptoms with Hospital Anxiety and Depression Scale (HADS-D). Patients with and without depressive symptoms were compared according to the prevalence of general risk factors for depression, comorbidities, PsA features and serum IL-6, TNF-α, and IL-17A.

Fifty-eight patient (38.7%) had a depressive mood. Depressive symptoms were associated with female sex (p = 0.03) and current smoking (p = 0.05). Patients with and without depressive symptoms did not differ for general risk factors for depression and comorbidities. Depressed patients had more frequently psoriatic nail disease (p = 0.02) and significant physical disability (HAQ-DI ≥ 0.5) (p < 0.01) and were more frequently in moderate or high disease activity according to DAPSA score (p = 0.01). Depressed patients had higher serum IL-6 (p < 0.01) and comparable serum IL-17A and TNF-α. A cutoff of 2.27 pg/ml of serum IL-6 had the best ability to predict an HADS-D ≥ 8 (AUC 0.666 ± 0.044; p < 0.01). Multivariate logistic regression analysis confirmed that serum IL-6 ≥ 2.27 pg/ml was independently associated with depressive symptoms (OR 3.5; CI 1.6-7.8; p < 0.01).

Higher serum Il-6 is associated with depressive symptoms. This association suggests a direct role of systemic inflammation in the modulation of mood in PsA patients. Key Points • High PsA disease activity and physical disability are associated with depression. • Higher serum levels of IL-6 are independently associated with depression in PsA. • IL-6 might play a direct role in the development of depression in PsA patients.