Depression in Psoriatic Arthritis: Dimensional Aspects and Link with Systemic Inflammation

Studying comorbidities in patients with psoriatic arthritis (PsA) provides a better understanding of the extended burden of the disease. Depression and anxiety are well recognized but understudied comorbidities in patients with PsA. The prevalence of depression is significantly higher in this patient population than in the general population, with far reaching consequences in terms of long-term quality of life. Over the past few years there has been an increasing interest in the link between inflammation and depression, with several novel studies being conducted. Recent evidence suggests a significant improvement of depression in PsA patients treated with biologic disease-modifying anti-rheumatic drugs (bDMARDs) as compared to conventional DMARDs. Depression in PsA is multidimensional, with recognized phenotypes, including cognitive disorder, alexithymia and anhedonia. The paucity of standardized, validated tools to screen these dimensional phenotypes remains an unmet need. Prevalence studies on depression in patients with PsA, mostly based on patient-reported outcomes, are only able to highlight the tip of the iceberg. A comprehensive, multi-disciplinary approach addressing the subdomains of depression is imperative for a better understanding of depression in PsA patients, as well as to find a way forward for improving their quality of life. In this scoping review, we explore existing evidence on the burden of depression in PsA patients, the link between inflammation and depression in these patients and the screening tools used to evaluate the subdomains of depression. Psoriatic arthritis (PsA) is a chronic, deforming arthritis associated with the skin condition psoriasis. A large number of patients with PsA are known to have another co-existing chronic disease, which adds to their overall disease burden and affects their quality of life. Depression is a common illness known to co-exist in about 20% of patients with PsA. Inflammation is a common factor between psoriatic arthritis and depressive disorders and is thought to play an important role in depression ocurring in these patients. Recent research in the field has revealed that different dimensions of depression, such as the inability to feel pleasure, loss of intellectual functions and difficulty identifying and expressing emotions, may contribute to the overall disease. It is important to screen for these dimensions while assessing PsA patients with depression. Most of the studies conducted to date have based the diagnosis of depression on self-reported questionnaires. In this article we describe the relation between inflammation and different dimensions of depression in patients with PsA and set out a feasible screening method for depression. A good understanding of depression in patients with PsA will be useful in designing treatment strategies.