Examination of the Psychometric Properties of the Headache Specific Locus of Control Scale
Grinberg, Amy S.
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Objective: To investigate the factor structure and psychometric properties of the Headache-Specific Locus of Control scale (HSLC) in clinical migraine populations. Participants and Methods: 695 adults with a diagnosis of migraine from five different research studies completed cross-sectional self-report measures including the HSLC and measures of headache related beliefs/cognitions (Headache Management Self-Efficacy, HMSE and the Pain Catastrophizing Scale, PCS), psychiatric symptoms (Generalized Anxiety Disorder 7-item Scale, GAD-7, Beck Anxiety Inventory, BAI, Patient Health Questionnaire, PHQ-9, PROMIS scales for anxiety and depression, Center for Epidemiologic Studies Depression Scale, CES-D, and the Beck Depression Inventory, BDI-II), and quality of life/disability (Migraine Specific Quality of Life Questionnaire, MSQL, and Migraine Disability Assessment, MIDAS). Results: Five HSLC components emerged from Horn's Parallel Analysis, Minimum Average Partials test, and Principal Components Analysis (eigenvalues: "Presence of Internal" = 5.71, "Lack of Internal" = 3.96, "Luck" = 2.87, "Doctor"= 2.02, and "Treatment"= 1.49). The 33 HSLC items demonstrated adequate internal consistency for total (alpha = .79) and subscale scores, (alpha's = .69 to .88). This study found preliminary evidence of convergent validity. For example, "Presence of Internal" was associated with higher self-efficacy (r = .21), whereas "Lack of Internal" (r = -.65), "Luck" (r = -.35) and "Doctor" HSLC (r = -.18) were all associated with lower self-efficacy (ps < .01). "Lack of Internal" (r = -.12), "Doctor" (r = -.20), and "Treatment" HSLC (r = -.12) were all associated with higher migraine related quality of life impairments (ps < .01). Preliminary evidence of discriminant validity was established; there were no significant differences in any HSLC subscale scores based on people's race (ps > .01). Conclusion: This study suggests that HSLC is more multidimensional than previous conceptualizations. Future research should continue to evaluate the factor structure of the HSLC in various headache populations.