Reliability and validity of the Turkish version of the morningness – Eveningness questionnaire

Background: People are divided into different chronotypes in relation to their circadian rhythm features. The Morningness–Eveningness Questionnaire (MEQ), developed by Horne and Östberg, was the first and is the most used questionnaire for determining the chronotype of people. The reliability and validity of MEQ were tested in this study due to some deficiencies and inconsistencies in previous reliability and validity studies for the Turkish versions of MEQ and deficiencies regarding the validity and reliability of other versions of MEQ. Subjects and Methods: MEQ was translated into Turkish based on the opinions of five academics who were experts in their respective fields and the suitability and content validity of the questionnaire were ensured. The Turkish MEQ was administered to 419 undergraduate students aged 18–34 years. Robust minimum rank factor analysis (MRFA) was used to reveal the construct validity of the questionnaire. Results: As a result of the analyses, the questionnaire was examined in three factors. None of the items were excluded from the study and all items were collected under three factors. The explained total variance value was 42.7%, and the factors explained 64% of common (shared) variance in MRFA. According to the reliability analysis, Cronbach's alpha value for the MEQ Turkish version was satisfactory for the overall questionnaire (0.765). Conclusions: The MEQ version developed in this study is more valid and reliable compared with other versions. However, these results support that a more detailed instrument for morningness and eveningness can be developed.