Our data from a unique cohort of physically healthy Syrian and Iraqi refugees (relatively young, similar trauma, timing of exposure and stress of migration, and timing of data collection within the first month of their arrival in the host country) showed a negative trend for IL-1β predicting PTSD, where lower concentrations of IL-1β were associated with greater severity of post-traumatic stress symptoms. This evidence concerns the gene IL1B and post-traumatic stress disorder.