Huang JH, et al. - In view of the observation that the G-allele of the -1019C/G (rs6295) promoter polymorphism of the serotonin receptor 1A (HTR1A) gene has an implication in anxiety and that low parasympathetic (vagal) tone is predictive of anxiety, researchers conduct a structural equation model (SEM) to investigate if the HTR1A rs6295 variant can affect anxiety by altering parasympathetic nervous activity. Findings reveal that by modulating parasympathetic tone, HTR1A -1019C/G polymorphism influences anxiety levels by modulating parasympathetic tone, providing a neurophysiological insight into the role of HTR1A in human anxiety.