NOS1 and Headache: In the study on the carriage of rs3782218 in the NOS1 gene, the data obtained were found to be consistent with the HWE law in group 1 (TTH and AH overlap syndrome)—χ2 = 0.016; p-value = 0.99, group 2 (AH without headache)—χ2 = 0.248; p-value = 0.88 and group 3 (control)—χ2 = 0.008; p-value = 0.1.