Reliability of the Spanish version of the Composite Scale of Morningness.

AIM: The aim of this study was to examine the reliability of the Spanish version of Composite Scale of Morningness (CSM) and its ability to measure the circadian typology. SUBJECTS AND METHODS: Voluntary and unpaid psychology students (N= 391; 132 men and 259 women), aged between 17 and 33, completed the questionnaire between the months of September and December. RESULTS: The total score was independent of age and gender, with a close to normal distribution and a non-significant negative skewness. The internal consistency was high (Cronbach's alpha= 0.87) and factor analysis extracted three factors labeled Time of Retiring (items 2 and 7), Activity Planning (items 8, 9, and 13) and Morning Affect (items 3-6, and 10-12). With the 10th and 90th percentiles as cut-off scores, scorers below 22 (N= 40; 10.2%) are classified as evening-types and scorers above 39 as morning-types (N= 28; 7.2%). CONCLUSION: The Spanish questionnaire shares most of the good psychometric properties of other versions of the CSM, and thus can be used for Spanish-speaking student samples. Nevertheless, further studies of normative data in workers and aged subjects are needed in order to validate CSM.