HTR3A and Anxiety: The first CpG in both the overall and long-lasting CpGs ranking was annotated to the serotonin receptor 3 A gene, HTR3A. Methylation at cg01586609 showed a slow decrease between the 4th therapy time point towards the beginning of the exposure followed by an abrupt increase after the peak of anxiety to reach a summit 24 h thereafter (Fig. 3).