Cross-Sectional Evaluation of the Psychometric Properties of the Headache-Specific Locus of Control Scale in People With Migraine.

Objective: This study aims to investigate the psychometric properties (component structure, reliability, and construct validity) of the Headache-Specific Locus of Control scale in several clinical migraine populations.

Background: Headache-specific locus of control beliefs may impact a person's behavioral decisions that affect the likelihood of migraine attack onset, emotional responses to migraine attacks, coping strategies used, and treatment adherence. The 33-item Headache-Specific Locus of Control scale is the most widely used measure of locus of control specific to headache yet psychometric evaluations remain limited.

Methods: Six hundred and ninety-five adults with a diagnosis of migraine from 5 different research studies completed cross-sectional self-report measures including the Headache-Specific Locus of Control scale and measures of quality of life and disability (Migraine-Specific Quality of Life Questionnaire and Migraine Disability Assessment).

Results: Five Headache-Specific Locus of Control components emerged from Horn's Parallel Analysis, Minimum Average Partial test, and Principal Component Analysis (eigenvalues: Presence of Internal = 5.7, Lack of Internal = 4.0, Luck = 2.9, Doctor = 2.0, and Treatment = 1.5). The 33 Headache-Specific Locus of Control items demonstrated adequate internal consistency for total (α = 0.79) and subscale scores (α's = 0.69 to 0.88). This study found preliminary evidence of convergent validity. For example, Lack of Internal (r = -0.12, P = 0.004), Doctor (r = -0.20, P < .001), and Treatment (r = -0.12, P = .004) beliefs were associated with higher overall migraine-specific quality of life impairments.

Conclusions: The Headache-Specific Locus of Control scale is a reliable and valid measure of headache-specific locus of control. Findings suggest that headache-specific locus of control is more multidimensional than previous conceptualizations and contribute to our understanding of control beliefs as a potential mechanism for migraine treatment.