Aggression predicts Cortisol Awakening Response in healthy young adults

It seems that aggressive behavior is negatively related to cortisol (C), but this relationship has been established considering the evening C levels. On the other hand, the relationship with the C awakening response (CAR) and the influence of gender and menstrual cycle phase are not well understood. This study analyzed this relationship in 83 women (38 in the luteal and 45 in the follicular phase of their menstrual cycle) and 20 men. CAR was assessed by measuring salivary free cortisol levels in samples taken immediately following awakening and 30, 45, and 60 minutes later. Additionally, participants completed a self-report of aggression. Men presented lower CAR than women in the luteal phase. Moreover, they also had higher levels of physical aggression than women, independently of their menstrual phase. Regarding the relationships between variables, in men general aggression and verbal aggression predicted the CAR. In women, verbal aggression predicted the CAR during the follicular phase, whereas anger and physical aggression were predictors during the luteal phase. Our data support the view that there is a negative relationship between C and aggressive behavior, even during the morning, this relationship being moderated by gender and menstrual cycle phase in the women. These findings may help improve our understanding of the biological mechanisms involved in violence.