Positive and negative affect and arousal: cross-sectional and longitudinal associations with adolescent cortisol diurnal rhythms.

Objectives: Psychobiological research with adolescent populations tends to focus on negative mood, stress, and psychopathology, but the role of positive emotions is insufficiently understood. The current study examines the relative contributions of both negative and positive affective experiences to the basal activity of the hypothalamic-pituitary-adrenal axis, measured by levels of cortisol across the waking day.

Methods: A sample of 315 ethnically and racially diverse high school students (mean age = 17.1 years, 73% female) completed a multiple-day naturalistic salivary cortisol protocol twice over a 5-year period. Along with each saliva sample, youth provided diary reports of their current mood states. Principal components analysis revealed four factors: high arousal positive affect (PA), low arousal PA, high arousal negative affect (NA), and low arousal NA.

Results: Multilevel growth curve models suggested that greater high arousal PA was associated with adaptive patterns of hypothalamic-pituitary-adrenal activity: steeper cortisol slope from waking to bedtime and lower evening cortisol, independent of NA. In addition, increases in high arousal PA over the 5-year follow-up period were associated with a steepening of the diurnal cortisol slope (β = -0.038, p = .009; negative values indicate the decrease of cortisol throughout the day) and lower evening cortisol levels (β = -0.661, p = .027) based on within-person fixed-effect regression analysis.

Conclusions: This study shows that high arousal PA, such as feeling alert and active, is associated with a steeper decline in cortisol throughout the day. Low arousal positive emotions did not display this relationship.