Figure 1a and Figure 1b show that the MCP-4/MCP-1 ratio for PTSD is significantly higher than healthy controls for both female and male PTSD patients. Consistently, Figure 1c shows that significant elevation of the MCP-4/MCP-4 ratio is observed when both male and female PTSD patients are grouped together. Statistically, Figure 1d shows that for both genders, the P-values are ca. ⩽0.05 over the entire circadian time period. Furthermore, by pooling all PTSD patients and comparing them with all healthy controls, the P-values for each time point across circadian time is ca. 0.001. Here, CCL2 is linked to post-traumatic stress disorder.