SLC6A3 and depressive symptom measurement: We found no significant relationship between striatal DAT SBR and the GDS-15 ‘depression’ factor (main effect across all time points: β=−0.06, 95% CI (−0.14 to 0.26), p=0.5; interaction with time: β=−0.06, 95% CI (−0.13 to 0.01), p=0.09) (online supplemental figure S2B).