Depression severity and discordance between fatigue patient-reported outcomes in people with multiple sclerosis

Objective: Fatigue and depression are common and disabling symptoms in people with Multiple Sclerosis (PwMS). This study aimed to examine the relationship between discordant fatigue measures and depression severity in PwMS. Methods: A retrospective analysis was conducted on 712 PwMS evaluated over 14 years at a comprehensive MS center. All participants completed the Fatigue Severity Scale (FSS), Modified Fatigue Impact Scale (MFIS), and Beck Depression Inventory (BDI) as part of routine clinical care. Fatigue score concordance was defined as both FSS and MFIS being above or below the threshold; discordance was defined as one above and one below. Statistical analyses compared demographic, clinical, and depression-related variables between groups. Results: Of the 712 patients (75.3% female; mean EDSS 2.8), 78.9% demonstrated concordant fatigue scores, while 21.1% showed discordance—most commonly with elevated MFIS and low FSS. The discordant group had significantly higher mean BDI scores (23.0 vs. 9.8; P < 0.0001) and elevated suicidality scores, despite similar clinical characteristics. Conclusions: PwMS with discordant fatigue profiles, particularly those with higher MFIS than FSS scores, exhibit significantly greater depressive symptoms. Discordance between fatigue measures may serve as a clinical marker for underlying depression, supporting the need for comprehensive psychosocial evaluation in this subgroup.