SLC6A3 and Apathy: Though motor symptoms increased over time and lower striatal DAT SBR was associated with worse motor symptoms across all time points (main effect: β=−1.30, 95% CI (−2.4 to -0.22), p=0.02) (online supplemental figure S2A), unlike apathy/anhedonia, this association did not strengthen over time (interaction: β=0.20, 95% CI (−0.25 to 0.65), p=0.4) (online supplemental figure S2A).