COMT and drug-induced dyskinesia: The most studied COMT SNP rs4680 has already been associated with motor fluctuations (Watanabe et al., 2003; Hao et al., 2014; Wu et al., 2014), dyskinesia (Watanabe et al., 2003; Bialecka et al., 2008; de Lau et al., 2012), and daytime sleepiness (Frauscher et al., 2004).