To evaluate the reproducibility of the scales, the intraclass correlation coefficient was calculated. Cronbach’s alpha was calculated to investigate the internal consistency of the scales. Values exceeding 0.70 are considered acceptable. Item-total correlation, adjusted for specific items, was also calculated as a measure of internal consistency. A correlation of at least 0.4 was assumed as a standard to provide internal consistency. Construct validity was evaluated with Spearman’s correlation coefficient among the scales and variables such as age, EDSS score, sex, and duration of disease. The psychometric properties of the Persian version of the PSQI were confirmed previously. The known-group validity was evaluated for each scale with an independent sample t-test to compare results between the MS and control groups. To evaluate the dimensionality of the questionnaires, confirmatory factor analysis was used. Acceptability of the questionnaires was evaluated with the following indices: possible and observed change, mean, floor or ceiling effects, and skewness. The floor and ceiling effects are based on the assumption that more than 15% of the participants obtain either the lowest or highest score on the questionnaire. An absolute skewness value of lower than 2 indicates normality. The effect size of the scales was also calculated using Cohen’s d.