When we look specifically into the literature for this immune marker, we see that lower levels of IL-8 have previously been associated with higher severity levels of depression in adult females (Kruse et al., 2021), more depressive symptoms over time in adolescent males (Moriarity et al., 2019), and with first episode or drug-free major depressive disorder in adulthood (Çakici et al., 2020; Zhu et al., 2022). This evidence concerns the gene CXCL8 and major depressive disorder.