While depression correlated with PTSD in those exposed to sarin in the Tokyo subway terrorist attack [54], depression is also observed in individuals exposed to OP pesticides [60,61] as well as those individuals exposed to sarin where red blood cell cholinesterase level is between 10% and 40% of control [66] raising the possibility that a cultural difference in Japanese people may have contributed to the depressive symptoms associated with PTSD [54]. This evidence concerns the gene BCHE and depressive symptom measurement.