COMT and 22q11.2 deletion syndrome: Because of COMT haploinsufficiency in 22q11DS and previously described findings of SPECT and PET studies (Boot et al., 2010, 2011b; Butcher et al., 2017; van Duin et al., 2018), we expected reduced D2/3R BPND in frontal brain regions compared to healthy controls (HCs), as a proxy marker of chronically increased extracellular frontal DA levels.