COMT gene and risk for Parkinson's disease: a systematic review and meta-analysis.

Several single-nucleotide polymorphisms (SNPs) in the catechol-O-methyltransferase (COMT) gene have been associated with the risk of developing Parkinson's disease (PD). We conducted a systematic review and a meta-analysis including all the studies published on PD risk related with COMT SNPs (mainly rs4680). We also reviewed the possible relationship of COMT SNPs with clinical, neuropharmacological, neurochemical, and neuroimaging features of PD.