ABSTRACT Objectives The objectives were to evaluate the prevalence of comorbidities at the time of multiple sclerosis (MS) diagnosis in a Finnish cross‐sectional cohort and to analyze whether comorbidities at diagnosis associate with clinical characteristics, treatment delays, initial disease‐modifying treatment (DMT) choice, DMT persistence, and disease activity. Methods Patients with relapsing‐remitting MS (RRMS) were recruited during their appointments at the neurology outpatient clinic of the Oulu University Hospital, Finland, between the years 2018 and 2022. The data was gathered from the hospital medical records. Results The study cohort consisted of 421 Finnish RRMS patients, of whom 51.8% had at least one or more comorbidity at the time of MS diagnosis. Depression (16.2%) and migraine (11.6%) were the most common comorbidities. Medium‐efficacy injectable DMTs (interferon‐β and glatiramer acetate) were associated with lower treatment persistence in patients with any comorbidity or psychiatric comorbidity during the 4‐year follow‐up. Among patients with psychiatric comorbidity, the rate of DMT discontinuation was high shortly after the DMT initiation, and the annualized relapse rate at the start of the DMT was higher compared with those without psychiatric comorbidity (1.3 SD 0.78 vs. 1.1 SD 0.74, p = 0.026). Conclusion Comorbidities, especially psychiatric diseases, are associated with lower persistence on injectable DMTs. As comorbidities complicate the treatment of RRMS, it is crucial to identify their role from early on.
Ahvenjärvi et al. (2026) studied this question.