Depressive symptoms linked to poorer remission odds in psoriatic arthritis, regardless of sex, German register finds

People with psoriatic arthritis who carry moderate or severe depressive symptoms are markedly less likely to reach minimal disease activity or remission after starting a new systemic antirheumatic therapy, according to an analysis of the German RABBIT-SpA register published in BMC Rheumatology. The association held across both sexes, and a formal statistical test found no evidence that the relationship differed between women and men. The study, based on 2,139 patients enrolled since the register began in May 2017, adds a large real-world dataset to a growing body of evidence linking mental health to how rheumatoid arthritis and psoriatic arthritis patients respond to treatment.

The register recruits patients from rheumatological practices and clinics throughout Germany at the start of a new systemic treatment, whether a biological or targeted synthetic drug or a conventional synthetic disease-modifying antirheumatic drug or non-steroidal anti-inflammatory drug. Physicians and patients fill out case report forms at recruitment, at three and six months, and then every six months for up to ten years. For this analysis, the researchers included all psoriatic arthritis patients enrolled through September 1, 2024 who had a baseline physician form and enough follow-up time to reach the six-month visit. Of 2,416 patients in the dataset, 277 had not yet reached six months of follow-up and were excluded, and 251 of the remaining 2,139 lacked a valid score on the screening questionnaire used to measure depressive symptoms.

Depressive symptoms were assessed with the WHO-5 Well-Being Index, a five-item screening instrument in which patients rate statements such as feeling cheerful, calm, active, rested and interested in daily life on a scale from never to all of the time. The item scores are summed and multiplied by four to yield a percentage score from 0 to 100, with higher values indicating higher well-being. Patients scoring below 29 were classified as having moderate or severe depressive symptoms, while those at 29 or above were classified as having none or mild symptoms. Among the 1,888 patients with a valid score, 29 percent fell into the moderate or severe category, and the burden was clearly uneven between the sexes: 34 percent of the 1,108 women versus 23 percent of the 780 men.

At baseline, patients with moderate or severe depressive symptoms looked different from their counterparts in ways that were largely consistent across sexes. Engagement in sports was less common, obesity somewhat more prevalent, and disease activity markedly higher. The proportion with five or more tender joints was higher in both women and men, as was the proportion with five or more swollen joints and the proportion with enthesitis, inflammation at the sites where tendons attach to bone. Mean DAPSA scores, a composite disease activity measure combining joint counts, patient assessments and C-reactive protein, were approximately six to seven points higher in both sexes. Comorbidity burden was greater, glucocorticoid use more frequent, and all patient-reported outcomes substantially worse, with the largest absolute differences seen for fatigue and disease impact scores.

To estimate the association between baseline well-being and remission, the researchers used logistic regression with the continuous WHO-5 score as the exposure, reporting odds ratios per 10-point increase. Confounder selection was guided by directed acyclic graphs, which mapped assumed causal relationships to identify which variables to adjust for. Both models included sex, age, body mass index, sports engagement, prior exposure to advanced therapies, number of comorbidities, symptom duration and type of inclusion therapy; the minimal disease activity model additionally adjusted for baseline values of that outcome’s components, and the DAPSA model for baseline DAPSA and related disease activity variables. Missing data were handled with multiple imputation using chained equations, generating 50 imputed datasets whose results were pooled with Rubin’s rules, and sensitivity analyses restricted to patients with observed WHO-5 scores produced closely consistent results.

In the adjusted analyses, each 10-point increase in baseline well-being was significantly associated with higher odds of minimal disease activity at six months, with an odds ratio of 1.10, and of DAPSA remission at both three and six months, with odds ratios of 1.08 and 1.14 respectively. The association with minimal disease activity at three months narrowly missed statistical significance, with an odds ratio of 1.06 and a p-value of 0.051. To test whether the association differed by sex, the models included a sex-by-well-being interaction term, and none of the four interaction terms reached significance, with all 95 percent confidence intervals including 1 and p-values of at least 0.29. The authors note that although exploratory subgroup estimates initially appeared larger in women, stratified estimates that differ in statistical significance are not equivalent to a formally demonstrated difference in effect.

The descriptive trajectories told a similar story. Among patients with no or mild depressive symptoms, 40 percent achieved minimal disease activity at three months and 29 percent sustained it at both time points, with an additional 14 percent newly reaching it by six months. Among those with moderate or severe symptoms, only 18 percent achieved minimal disease activity at three months, 10 percent sustained remission, and 9 percent newly achieved it between three and six months. The pattern was evident in both sexes: among women with no or mild symptoms, 34 percent reached minimal disease activity at three months and 22 percent sustained remission, compared with 15 and 7 percent among women with moderate or severe symptoms; among men, the corresponding figures were 47 and 37 percent versus 24 and 17 percent. Overall rates were lower in women than in men regardless of symptom category.

A crucial sensitivity analysis complicates the interpretation. When the researchers replaced the composite outcomes with objective-only indicators, swollen joint count of one or less in place of minimal disease activity and C-reactive protein normalization in place of DAPSA remission, baseline well-being showed no association with joint-count response at either timepoint, and was inversely associated with C-reactive protein normalization at six months, with an odds ratio of 0.91. This indicates that the association with the composite outcomes is predominantly attributable to their patient-reported components, such as pain, patient global assessment and function, rather than to objective inflammatory improvement. The authors are explicit that the findings reflect an association between depressive symptoms and how patients experience and report their symptom burden, not evidence that depressive symptoms influence the underlying inflammatory disease process.

Several limitations frame the results. Depression was not formally diagnosed; the WHO-5 is a screening instrument, not a diagnostic tool, and earlier register analyses indicated substantial underreporting of documented depression even among patients with severe symptoms. The minimal disease activity definition was adapted from standard criteria to match available registry data, substituting body surface area for the psoriasis severity index and numeric rating scale cut-offs for visual analogue scale cut-offs, and this adaptation has not been separately validated. The exposure was measured only at baseline, although the relationship between depressive symptoms and disease activity is likely bidirectional, and despite adjustment for confounders identified by the causal graphs, the authors cannot exclude confounding by indication, since patients with moderate or severe symptoms differed across multiple baseline characteristics. Residual confounding from unmeasured variables also cannot be excluded.

The authors conclude that routine screening for depressive symptoms should be considered in psoriatic arthritis management to identify patients at risk of suboptimal treatment response, and suggest that mental health be treated as an integral component of care. They note that addressing depressive symptoms through timely referral for psychological or pharmacological interventions may improve mental health, but whether this could also improve response to antirheumatic therapy has not been demonstrated by this study and remains to be tested in interventional trials. Future work, they write, should employ repeated measures of both depressive symptoms and disease activity to assess the direction and temporality of their association, use larger multi-cohort collaborations to adequately power tests of effect modification by sex, and conduct randomized interventional studies with disease activity or remission as secondary endpoints.

Subject of Research: The association between depressive symptoms and achievement of remission in psoriatic arthritis patients starting new systemic therapy, analyzed in the RABBIT-SpA register.

Article Title: Depressive symptoms are associated with achieving remission in PsA patients – an analysis from the RABBIT-SpA register

Article References: Reich, A., Weiß, A., Lindner, L., Feuchtenberger, M., Dahmen, G., Lorenz, H.-M., Baraliakos, X., & Regierer, A. C. (2026). Depressive symptoms are associated with achieving remission in PsA patients – an analysis from the RABBIT-SpA register. BMC Rheumatology, 10(1), Article 79. https://doi.org/10.1186/s41927-026-00707-y

Image Credits: AI Generated

DOI: 10.1186/s41927-026-00707-y

Keywords: psoriatic arthritis, depressive symptoms, WHO-5 Well-Being Index, minimal disease activity, DAPSA remission, RABBIT-SpA register, sex differences, logistic regression, patient-reported outcomes, observational cohort, rheumatology, mental health