Background Post-traumatic stress disorder (PTSD) is a mental disorder with delayed or chronic onset caused by unusual,threatening,or disastrous psychological trauma,and it is an important manifestation of post-disaster mental and behavioral disorders.Studies have shown that IL-6 is a cytokine associated with PTSD occurrence.This study aimed to explore the role of cytokine and ethnicity in the pathogenesis of PTSD by examining levels of serum cytokines IL-2,IL-6,IL-8,TNF-α,and cortisol in PTSD patients of Li and Han ethnic groups.Methods Levels of serum cytokines IL-2,IL-6,IL-8,TNF-α,and cortisol were examined by enzyme-linked immunoabsorbent assay (ELISA) method and assessed by PCL-C scale among 30 PTSD patients of Han ethnicity and 30 of Li ethnicity,and compared with 30 normal controls of Han and Li ethnicity,respectively.Results PTSD patients of Li ethnicity scored higher than PTSD patients of Han ethnicity,and normal controls of Li and Han ethnic groups in each of the re-experiencing,avoidance/numbing,and hyperarousal symptoms.The differences reached statistical significance (P ＜0.05).In PTSD patients of Li ethnicity compared to patients of Han ethnicity and normal controls of either Li or Han ethnicity,the levels of IL-2,IL-6,IL-8,and TNF-α were higher,and the level of cortisol was lower.Conclusions There are ethnic differences in re-experiencing,avoidance/numbing,and hyperarousal symptoms among PTSD patients.The levels of serum cortisol and cytokines are strongly associated with the race.