Individual differences in the activation and regulation of the limbic -hypothalamic -pituitary -adrenal axis after stress: Implications for emotion regulation research.

Abstract

The purpose of this study was to create a novel individual differences approach to examine LHPA differences among children with high levels of proactive and reactive aggressive behaviors as well as children displaying high levels of internalizing behavior problems. Participants included 73 children (33 girls) ranging from 6 to 7 years of age participating in a large NIMH study of young children at risk for conduct problems. After a 30-minute baseline activity participants were randomly exposed to a fear (n=33), frustration (n=32), or a non-stress (n=8) condition. Participants then watched a neutral cartoon for 60 minutes. A dense cortisol sampling procedure was used to create detailed individual activation curves. A total of 5 cortisol samples were taken before the stress condition and 12 samples were taken post-stress at 5 minute intervals. Behavioral measures were obtained using the Child Behavior Checklist and the Aggression Behavior Teacher Checklist. Individual cortisol responses to the stressors varied significantly, specially in regards to the timing of the peak cortisol response. This variability was mostly determined by stress modality with those children exposed to the fear condition reaching peak cortisol on average at 25 minutes post stress and those exposed to the frustration condition peaking at 45 minutes post stress. No gender differences in LHPA-axis functioning was found. Children with high levels of reactive aggression displayed significantly higher peak cortisol levels, steeper activation curve, and total cortisol produced than children with high levels of proactive aggression and non-aggressive children. There were no clear differences in cortisol determinations between children with high levels of proactive aggression and non-aggressive children. Children with high levels of internalizing problems also displayed an overactive cortisol response, including shorter time to reach peak cortisol levels, steeper activation curve, and higher total cortisol production. Our results also suggest that, when compared to the traditional group-based cortisol determinations obtained at specific pre-defined intervals, an individual differences approach provided more robust associations between LHPA axis functioning and conduct problems.