Allelic Variation in the Serotonin Transporter Gene-Linked Polymorphic Region (5-HTTLPR) and Cardiovascular Reactivity in Young Adult Male and Female Twins of European-American Descent

Abstract

To examine the effect of length variation in the serotonin transporter gene-linked polymorphic region (5-HTTLPR) on individual differences in cardiovascular response to psychological challenge. Heart rate (HR) and systolic and diastolic blood pressure (SBP, DBP) responses to computerized versions of two psychological challenges, the Stroop Color-Word Interference Test and mental arithmetic, were measured among 131 monozygotic (MZ) and 60 dizygotic (DZ) male or female (same-sex) European-American twin pairs. Among the 382 participants, 140 were homozygous for the "long" allele (l/l) at 5-HTTLPR, 61 were homozygous for the "short" allele (s/s), and 181 participants had one long and one short allele (l/s). Association and sib-pair analyses were performed to characterize genetic associations. In the full sample, 5-HTTLPR was associated with HR reactivity to psychological challenge, albeit in interaction with sex. Task-elicited HR responses of women homozygous for the short allele were significantly greater than among: a) men of the same genotype; and b) women having either one (l/s) or two (l/l) long alleles at 5-HTTLPR. SBP and DBP responsivity was unrelated to genotype. These results were corroborated on reanalysis in two genetically independent subsamples. Variability at 5-HTTLPR also predicted HR reactivity in sib-pair analyses among DZ twins. These results suggest that the commonly observed sex difference in HR reactivity may be, in part, genetically mediated and perhaps occur only among individuals homozygous for the short allele at 5-HTTLPR.