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 < or = .04) and to a neutral expression (at Pz: P < or = .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 < or = .02; Tukey honestly significant difference, SS vs LL, P < or = .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, P < or = .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 < or = .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.