The CB1 gene, CNR1 mapped to chromosome 6q14-15, was linked to migraine through haplotypic tagging with high significance (p=0.008) and indicative of a genetic effect altering trigeminovascular activation.55 The strongest linkage was to HT6 haplotype (p=0.002), which correlated highly with migraine symptoms of photophobia > nausea > disability. Here, CNR1 is linked to Photophobia.