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.