To investigate whether the association between depression and inflammatory joint disease (IJD; rheumatoid arthritis [RA], psoriatic arthritis [PsA], ankylosing spondylitis/spondyloarthropathies [AS], and juvenile idiopathic arthritis [JIA]) is affected by the severity or treatment-resistance of depression.

Parallel cohort studies and case-control studies among 600,404 patients with a depressive episode identified in Swedish nationwide administrative registers. Prospective and retrospective risk for IJD in patients with depression was compared to matched population comparators, and the same associations were investigated in severe or treatment-resistant depression. Analyses were adjusted for comorbidities and sociodemographic covariates.

Patients with depression had an increased risk for later IJD compared to population comparators (adjusted hazard ratio (aHR) for any IJD 1.34 [95% CI 1.30–1.39]; for RA 1.27 [1.15–1.41]; PsA 1.45 [1.29–1.63]; AS 1.32 [1.15–1.52]). In case-control studies, patients with depression more frequently had a history of IJD compared to population controls (adjusted odds ratio (aOR) for any IJD 1.43 [1.37–1.50]; RA 1.39 [1.29–1.49]; PsA 1.59 [1.46–1.73]; AS 1.49 [1.36–1.64]; JIA 1.52 [1.35–1.71]). These associations were not significantly different for severe depression or TRD.

IJD and depression are bidirectionally associated, but this association does not seem to be influenced by the severity or treatment resistance of depression.