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: Pless than or equal to.04) and to a neutral expression (at Pz: Pless than or equal to.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, Pless than or equal to.02; Tukey honestly significant difference, SS vs LL, Pless than or equal to.01). An analysis of covariance showed that neither the type of expression nor the genotype per se influenced the N400 amplitudes, but a significant expression X genotype interaction was found (F-4.72 = 3.57, Pless than or equal to.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, Pless than or equal to.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.