Genetic contributions to acute autonomic stress responsiveness in children

Identification of genetic factors that influence stress reactivity is important in order to link environmental demands, particularly adversity to disease outcome. There is ample literature on genetic contribution to the endocrine stress response, while evidence for genetic contribution to individual differences in autonomic nervous system function is sparse and produced conflicting results. Here, we investigated the influence of two polymorphisms in the Catechol-o-methyltransferase (COMT) and serotonin transporter (5-HTT; SCL6A4) gene. We examined the autonomic stress response to the Trier Social Stress Test for Children in 115 children. Salivary α-amylase (sAA) was obtained prior to the stressor and repeatedly during recovery as a marker of autonomic reactivity. Furthermore, heart rate (HR) and heart rate variability (HRV) were monitored continuously. We found differences in ANS stress response associated with each polymorphism (all p<.05). Children with the L variant of 5-HTTLPR showed a higher increase and sharper recovery of sAA in response to stress than those with S variants. For HR, we found differences associated with COMT, i.e. children carrying at least one met allele showed lower mean HR increase and slower HR recovery in response to the stressor compared to those with two val alleles (p<.001) as well as a significant decrease in heart rate variability (p<.05). Our findings indicate that these two polymorphisms do indeed influence the ANS response to stress. This study provides further evidence for the crucial role of genetic factors in the modulation of differences in the acute stress response during childhood.