SST and psychiatric disorder: However, somatostatin-expressing (SST+) and vasoactive peptide-expressing (VIP+) interneurons contribute substantially to regulating GABAergic inhibition in the cortex (Rossignol, 2011; Pfeffer et al., 2013; Veit et al., 2017) and dysfunction of these interneurons are associated with psychiatric disorders (Rossignol, 2011; Fung et al., 2014).