GAD1 and Alzheimer disease: One notable gene associated with CDR was GAD1, encoding the GABA‐synthesizing enzyme, glutamic acid decarboxylase, whose expression monotonically decreased over the CDR continuum, in line with deficits in inhibitory neurotransmission seen in AD (Figure 5E, n = 110, Limma logFC = −0.34, FDR = 0.001) (Xu et al. 2020).