PET studies using radioligands for DRD1 have shown some promise as a means of researching the DA system in psychiatric diseases, ideally with higher selectivity radioligands, so that DRD1 can be evaluated as a candidate biomarker for disease and ultimately for treatment (Cervenka, 2019; Stenkrona et al., 2019; Yokokura et al., 2020). Here, DRD1 is linked to psychiatric disorder.