Another group Corominas et al. 2009 analysed 50 tag SNPs in 8 genes from the dopaminergic system: DRD1, DRD2, DRD3, DRD5, DBH, COMT, SLC6A3 and TH in two case control populations of Spanish origin and found no evidence of robust genetic association of any of these genes with migraine. This evidence concerns the gene DRD1 and migraine disorder.