Circadian variation of mood: comparison between different chronotypes

For the investigation of a circadian pattern in the positive (PA) and negative affect (NA) and a comparison between the chronotypes, 28 medical students (22 +/- 2.5 years) answered initially the Morningness-Eveningness Questionnaire (MEQ) and then the PANAS (Positive and Negative Affect Schedule) and two visual analogue scales (VAS) every three hours during wakefulness for two weeks. The words we chose to represent the PA and NA in the VAS were "attentive" and "upset". Considering the Cosinor method analyses for the PANAS and the VAS results, 85.71% of subjects displayed significant circadian variation of PA (for p < 0.05). For NA, 25% in the PANAS results and only 14.28% in the VAS displayed a circadian pattern. There was a significant correlation between MEQ scores and acrophases of the PA measured with the PANAS (r = -0.61, p < 0.001) and with the VAS "attentive" (r = -0.69, p < 0.001). This data confirmed literature reports that there is a circadian pattern in the PA rhythm, but for NA the absence of a circadian pattern is not so well established. The significant correlation between MEQ scores and acrophases of PA support the idea that the PA variation occurs in a continuum between the two extreme chronotypes. The results also show that the PANAS and the VAS are in agreement and are equally sensitive in detecting a circadian pattern in the positive affects.