Psychometric properties of the stagnation scale in medication overuse headache patients

Background: Medication-overuse headache (MOH) is often comorbid with emotional disturbances, contributing to poorer outcomes. The aims of the present study were to assess the psychometric properties of the Stagnation Scale in a sample of MOH patients, and to compare two factor models: a three-factor model reported in previous studies and a proposed bi-factor model. Methods: Consecutive adult outpatients (N = 310) admitted to the Regional Referral Headache Centre of the Sant'Andrea Hospital in Rome (Italy) were administered the Stagnation Scale and two questionnaires measuring depression and perceived disability. Results: The original three-factor model demonstrated an adequate fit to the data (chi(2)(101) = 238.70; p < 0.001; Root Mean Square Error of Approximation [RMSEA] = 0.07; 90% CI of RMSEA = 0.06/0.08; Comparative Fit Index [CFI] = 0.98; Weighted Root Mean Square Residual [WRMR] = 0.75). However, the bi-factor model had a comparable or even better fit, with a RMSEA of 0.05 (90% CI: 0.04/0.07), providing strong evidence for an absolute fit to the data (chi(2)(88) = 161.43; p < 0.001; RMSEA = 0.05; 90% CI of RMSEA = 0.04/0.07; CFI = 0.99; WRMR = 0.56). The stagnation general factor and all the group factors correlated significantly and positively with convergent measures. Conclusions: There is support for the use of the Stagnation Scale in MOH patients, with the goal of better understanding the role of psychological factors in the evolution and course of the disorder.