SLC6A2 and Anxiety: For this purpose, we (1) experimentally analyzed which microRNAs regulated SLC6A2 expression, (2) studied which single-nucleotide polymorphisms (SNPs) of microRNA genes regulating SLC6A2 expression were associated with PD and trait anxiety, (3) experimentally analyzed whether the risk genotype modulated expression of its microRNA and whether this microRNA regulated other anxiety candidate genes, and (4) studied whether the risk genotype modulated sympathetic noradrenergic central fear processing and peripheral cardiovascular parameters.