Influence of the serotonin transporter promoter gene and shyness on children's cerebral responses to facial expressions

Background: Childhood shyness can predate social anxiety disorder and may be associated with biased discrimination of facial expressions of emotions. Objective: To determine whether childhood shyness, or the serotonin transporter promoter polymorphism genotype, can predict participants' visual event-related potentials in response to expressions of children of similar ages. Design: Study group drawn from an inception cohort of 149 subjects characterized 1 year before the present study by their degree of shyness. Setting: Third- and fourth-grade schoolchildren. Participants: Forty-nine of the inception cohort children, randomly selected. Main Outcome Measures: Latencies and amplitudes of the N400 waveform in response to happy, neutral, and angry expressions. Results: Shyness predicted significantly smaller N400 amplitudes in response to anger (at Pz: P≤.04) and to a neutral expression (at Pz: P≤.047). Shyness was significantly different across the 3 genotypes, the SS genotype being associated with higher shyness levels (analysis of variance: F_2,42=4.47, P≤.02; Tukey honestly significant difference, SS vs LL, P4,72=3.57, P≤.01), sustained by the difference in amplitude of the SS and S carrier subjects compared with the LL subjects when exposed to the anger expression (Tukey honestly significant difference, P≤.02). Conclusion: Children who manifest higher levels of shyness or have 1 or 2 copies of the short allele of the serotonin transporter promoter gene appear to have a different pattern of processing affective stimuli of interpersonal hostility.