The Association Between Psoriasis, Psoriatic Arthritis, and Fibromyalgia Syndrome: Effects on Treatment—A Population-Based Study

<i>Background and Objectives:</i> To examine the prevalence of fibromyalgia syndrome (FMS) in patients with psoriasis (PsO) and psoriatic arthritis (PsA) and its impact on treatment patterns and biologic therapy adherence. <i>Materials and Methods:</i> This retrospective cohort study utilized electronic health records from the Meuhedet Health Maintenance Organization in Israel between 2000 and 2020. PsO patients were matched 1:4 with controls by age, sex, and ethnicity. We assessed FMS prevalence, comorbidity burden, and treatment patterns. Cox regression and linear models evaluated the association between FMS and biologic switching and duration, adjusting for confounders. <i>Results</i>: Among 61,003 PsO patients and 244,012 controls, FMS prevalence was higher in PsO (3.3% vs. 2.3%, OR = 1.45, 95% CI: 1.38-1.53, <i>p</i> < 0.001). Among PsO patients, those with FMS were predominantly female (81.1% vs. 49.8%, <i>p</i> < 0.001) and had a higher prevalence of PsA (33.6% vs. 7.7%, <i>p</i> < 0.001). They received biologics more frequently (10.2% vs. 2.7%, <i>p</i> < 0.001) and were more likely to require multiple biologic lines (4.2% vs. 0.7%, <i>p</i> < 0.001). In PsA patients receiving biologics, FMS was associated with reduced survival on first-line therapy (6.1 vs. 10.1 years), increased switching risk (HR = 1.82, 95% CI: 1.42-2.35), and shorter treatment duration (B= -0.97 years, <i>p</i> = 0.001). <i>Conclusions</i>: In PsO patients, especially those with psoriatic arthritis, FMS is linked to greater treatment complexity and shorter biologic therapy survival, underscoring the need for tailored management strategies.