When testing for specificity of the above findings by controlling for each other impact in dyskinesia- and parkinsonism-related neurotransmitter systems using multiple linear regression, we found that among both significant associations between dyskinesia-related grey matter alterations and dopaminergic neurotransmitter systems, the dopamine transporter survived at a marginal significance level (P = 0.070). This evidence concerns the gene SLC6A3 and Parkinson disease.