The Relationship between Depression, Anxiety, Fatigue, and the Symbol Digit Modalities Test in Persons with Multiple Sclerosis

INTRODUCTION: Cognitive impairment, fatigue, and neuropsychiatric symptoms are commonly intertwined in multiple sclerosis. The multifactorial etiology of these disease-related symptoms has not been delineated clearly. This study aimed to investigate the relationship between fatigue, anxiety, depression, and cognitive function, as assessed by Symbol Digit Modalities Test (SDMT), in people with multiple sclerosis (pwMS).
METHODS: The oral version of the SDMT was used to measure cognitive function, the Hospital Anxiety and Depression Scale (HADS) for depression and anxiety, and the shortened version of the Modified Fatigue Impact Scale in MS (MFIS-5) for fatigue.
RESULTS: This single-center study included 269 pwMS (206 female, mean age: 33.66±9.57, mean education years: 11.97±3.5). The demographic and clinical outcomes were collected retrospectively. The hierarchical regression analyses demonstrated that the model was significant and explained the 44% of the variance (R2=0.44). The SDMT scores were not associated with fatigue, depression, and anxiety symptoms. Longer disease duration, fewer education years, and younger age were also independently associated with lower SDMT scores. PwMS with cognitive impairment (CI) (15.6%) and without CI differ significantly in disability level, age, HADS-depression score, and subscores and overall score of MFIS-5 (p<0.05).
DISCUSSION AND CONCLUSION: In conclusion, lower education level, longer disease duration, and older age were associated with lower information processing speed in pwMS. No associations were found between SDMT and fatigue, anxiety, or depression levels.