P2RX7 and Anxiety: However, to date, only very few studies investigating the role of the P2RX7 gene in anxiety or anxiety disorders have been conducted, and even those focused primarily on other phenotypes, were carried out in small samples, and with a candidate variant approach focusing on a very small number of preselected polymorphisms, and while some of them reported a trend40 or a significant association25 of individual candidate variants with anxiety-related phenotypes, none of them considered the effect of stress.