Serotonin transporter promoter region (5-HTTLPR) polymorphism predicts resting respiratory sinus arrhythmia.

Respiratory sinus arrhythmia (RSA) is often conceptualized as an index of physiological flexibility that has been related to emotion regulatory capacity. Although behavioral genetics research indicates that RSA is partly heritable, relatively few molecular genetics studies have been conducted. We examined whether the serotonin transporter promoter region (5-HTTLPR) polymorphism was associated with resting RSA among healthy young adults (N=71). Short 5-HTTLPR allele carriers had significantly lower resting RSA than long 5-HTTLPR homozygotes. Genotype explained 5% of the variance in resting RSA. Although firm conclusions depend on further study, the short allele of the 5-HTTLPR polymorphism may contribute to individual differences in RSA and its behavioral correlates.