Moreover, in line with the study on GAD 65 and GAD 67 gene expression in elderly schizophrenics [14], we found a positive correlation between the duration of illness and GAD-ir neuropil density in BD patients in one of the investigated PFC regions (namely in the left OFC; r = 0.71, P = 0.047). The gene discussed is GAD2; the disease is Behcet disease.