Preliminary findings for the validity of the Morningness-Eveningness-Stability Scale improved (MESSi): Correlations with activity levels and personality.

Aim of the present study is an additional validation of the Morningness-Eveningness-Stability Scale improved (MESSi). We screened a total of 97 German students using the reduced Morningness-Eveningness Questionnaire (rMEQ) to identify a subsample (N = 42) of definite morning and evening types (31% males, mean age: 24.8 ± 5.8 years). The participants provided information about their sleep-wake rhythm (diary), personality traits (questionnaire) and experienced actigraphic monitoring. Correlations of the MESSi components "Morning affect subscale" (MA) (r = 0.91, p < 0.01) and "Eveningness subscale" (r = -0.87, p < 0.01) with the rMEQ showed good convergent validity. MA was also significantly negatively correlated with the acrophase and the midpoint of sleep as measured by actigraphy.