The interpretation of this pattern of association in the Hamza et al. [7] study is not straightforward: while controls who carried the rs4998386-T allele were heavier coffee drinkers than noncarriers, there was a nonsignificant association between rs4998386-T and coffee in the opposite direction among PD patients, therefore suggesting that GRIN2A may play a role in coffee drinking behaviour with opposite effects in healthy subjects and PD cases. This evidence concerns the gene GRIN2A and Parkinson disease.