An animal study showed that CUMS depressed mice had higher levels of CD45+ compared to normal mice.[39] Another clinical study in the United States demonstrated that after adjusting for sociodemographics, smoking, and substance use, patients with PTSD had a significantly higher proportion of CCR7-CD45RA + CD27-CD28- to CCR7 + CD45RA + CD27 + CD28 + than the non-PTSD group (β 1.52, 95% CI 0.56–2.48).[40] These findings support the association of CD28 and CD45RA with psychiatric disorders and indirectly suggest that CD28 + CD45RA + CD8br %T cell may be a potential risk factor for AN. This evidence concerns the gene CCR7 and post-traumatic stress disorder.