Functional polymorphisms in COMT and SLC6A4 genes influence the prognosis of patients with medication overuse headache after withdrawal therapy

Background and purpose It is currently unknown if common genetic variants influence the prognosis of patients with medication overuse headache (MOH). Here the role of two common single nucleotide polymorphisms in the COMT gene (rs4680 and rs6269), as well as the STin2 variable number tandem repeat (VNTR) polymorphism in the SLC6A4 gene, were evaluated as predictors for long‐term outcomes of MOH patients after withdrawal therapy. Methods Genotyping was conducted by polymerase chain reaction (PCR), PCR restriction fragment length polymorphism analysis or real‐time PCR allelic discrimination assay on genomic DNA extracted from peripheral blood. Gene variants association was evaluated by logistic regression analysis adjusted for clinical confounding factors, and the threshold of statistical significance for multiple testing was set at P