We examined the circadian rhythm of two basic dimensions of mood—Positive Affect (PA) and Negative Affect (NA). Subjects were 196 college students in two studies who completed a mood rating form approximately seven times a day for 1 week. Significant diurnal variation was found to exist in overall Positive Affect, and in four component content areas, but not in Negative Affect. Specifically, all components of PA rose sharply from early morning until noon, remained relatively constant until 9 p.m., and then fell rapidly. The rise and fall of PA were quite robust across subjects, but the apparently static level of PA from noon to 9 p.m. was shown to result from averaging across marked individual differences in the time of peak PA. Various potential sources of these individual differences—morningness-eveningness, introversion-extraversion, and neuroticism/dysphoria—were investigated. Neither of the personality variables accounted for the significant variation in diurnal mood patterning, but clearly defined morning and evening types did show different patterns. Possible links between the mood pattern obtained and biologically based circadian rhythms, which have been postulated to be dysregulated in depression and mania, are discussed.
Available at: http://works.bepress.com/lee_anna_clark/12/