SLC6A3 and Cognitive impairment: Examining the entire cohort (i.e., excluding MRI variables) and including only patients who were cognitively intact at baseline (N = 394), baseline predictors of incident cognitive impairment (based on site investigator diagnosis) were lower CSF Aβ 1–42, lower ipsilateral caudate DAT availability, COMT val158met (val/val genotype), and BDNF val66met (val/val genotype), see S3 Table.