The Impact of Multiple Sclerosis Symptom Severity on Quality of Life: The Mediating Role of Illness Perception and the Moderating Role of Cognitive Fusion

Abstract

This study aimed to examine whether illness perception mediates the relationship between MS symptom severity and quality of life, and whether cognitive fusion moderates this mediating pathway. In this cross-sectional descriptive-correlational study, 357 individuals with MS in Tehran completed the MSIS-29, Brief Illness Perception Questionnaire, WHOQOL-BREF, and the Cognitive Fusion Questionnaire. Data were analyzed using Pearson correlations and a moderated mediation model via PROCESS macro version 4.2. Symptom severity showed significant positive correlations with illness perception (r = .65, p < .001) and cognitive fusion (r = .32, p < .001), and a significant negative correlation with quality of life (r = –.67, p < .001). Illness perception mediated the effect of symptom severity on quality of life; however, this indirect effect was significant only at low levels of cognitive fusion (b = –.17, p = .028) and nonsignificant at moderate and high levels. Illness perception and cognitive fusion play central roles in shaping quality of life in MS. High cognitive fusion diminishes the impact of modifying illness perceptions; thus, interventions should prioritize reducing cognitive fusion before targeting illness perceptions.