Health Locus of Control and Its Relationship with Quality of Life and Functioning in Multiple Sclerosis: Exploring the Mediating Role of Self-Efficacy

Background/Objectives: Health locus of control (LOC) refers to one’s perceptions of who or what controls one’s health. Recent evidence has found that chance LOC (CLOC) is associated with improved quality of life (QoL) in multiple sclerosis (MS). The purpose of the current study was to identify mediators and moderators of the LOC-QoL relationship in MS. Methods: For this study, 5266 participants with MS completed a questionnaire pack that included the Multidimensional Health Locus of Control Scale, the Unidimensional Self-Efficacy Scale for MS (USE-MS), and the World Health Organization Quality of Life Scale—BREF (WHOQoL-BREF). The relationship between LOC and QoL was examined within a structural equation model (SEM). Results: In the total sample, self-efficacy was found to fully mediate the relationship between LOC and QoL for both internal (ILOC) and CLOC orientations. Powerful others LOC (PLOC) had no association with QoL. The same results were found for the relationship of LOC to functioning. In the secondary progressive MS subgroup, the relationship between CLOC and QoL was only partially mediated by self-efficacy. Conclusions: LOC influences QoL through its impact on self-efficacy, one of several potentially mediating factors between LOC and QoL in MS. Disability did not moderate the associations of LOC, but moderation of the CLOC-QoL relationship by disease subtype was found. Psychological training to improve self-efficacy in MS may be particularly useful in those subgroups where LOC-QoL is largely mediated by self-efficacy.