The Association Between the Occurrence of Sensory Integration Disorders, Depression, and Chronic Fatigue in Patients with Relapsing–Remitting Multiple Sclerosis

Background/Objectives: Multiple sclerosis (MS) is a chronic neurological disease associated not only with motor dysfunction but also with non-motor symptoms such as depression and MS-related fatigue (MSRF). Sensory integration disorders (SID) in MS remain poorly characterized. This study aimed to evaluate the association between SID and depression, MSRF, disability level, disease duration, and disease activity in patients with relapsing–remitting MS (RRMS). Methods: A total of 205 patients with RRMS were assessed using the Daniel Travis sensory integration questionnaire, Beck Depression Inventory (BDI), EDSS, FSMC fatigue scale, and MRI T2-lesion burden. Due to non-normal distribution, non-parametric statistical tests were applied with significance set at p < 0.05. Results: Statistically significant associations were identified between SID and depressive symptoms. Compared with patients without depression, individuals with mild to severe depression showed significantly higher impairment in under-responsiveness/sensory seeking (p = 0.040), sensory discrimination (p = 0.017 for mild; p = 0.011 for severe), sensory-based motor abilities (p = 0.007 for severe), and social–emotional functioning (p = 0.006 for mild; p = 0.014 for severe). Higher disability (EDSS > 3) was associated with impaired sensory discrimination (p = 0.013) and reduced motor abilities (p = 0.000). Longer disease duration was linked to poorer general sensory modulation (≤5 vs. 5–10 years p = 0.038; ≤5 vs. >10 years p = 0.037) and reduced motor abilities (>10 years p = 0.042). Increased disease activity (1 or ≥2 relapses/year) correlated with more severe under-responsiveness/sensory seeking (p = 0.039) and worse social–emotional functioning (p = 0.025 and p = 0.007). No significant association was found between SID and MSRF or MRI T2-lesion count. Conclusions: In conclusion, sensory integration disorders in RRMS are strongly associated with depression, disability level, disease duration, and relapse rate, but not with MSRF. SID assessment may provide additional insight into non-motor symptom burden and disease progression.