RGS2 and post-traumatic stress disorder: The majority of single nucleotide polymorphism (SNP) associations with PTSD demonstrate increased risk, but some such as variants in RGS2, demonstrate a differential susceptibility (i.e., some genotypes increase risk while others promote resilience).[109, 110] While the findings of these studies suggest the presence G×E interactions in PTSD, the power of these studies is severely limited by small sample size.