Several chromosomal regions may be involved in the development of mood disorders (Caspi et al., 2003; Roceri et al., 2004), such as purinergic receptor family member P2X7 (P2rx7) gain-of-function polymorphism (Czamara et al., 2018; Wingo et al., 2021), the role of which in the development of major depression remains controversial (Viikki et al., 2011; Feng et al., 2014). The gene discussed is P2RX7; the disease is major depressive disorder.