We found that out of 17 different cytokines and chemokines, elevated chemokine MCP-4 (monocyte chemoattractant protein-4; CCL11) and reduced chemokine MCP-1 (monocyte chemoattractant protein-1; CCL2) appeared to significantly distinguish PTSD subjects from healthy controls. This evidence concerns the gene CCL11 and post-traumatic stress disorder.