Interestingly, elucidating the role of the cholinergic system in the etiology of psychosis has been aided by studies into Alzheimer's disease where the CHRM1/CHRM4 partial agonist Xanomeline can reduce psychotic symptoms (Bymaster et al., 1997; Shekhar et al., 2008). This evidence concerns the gene CHRM4 and early-onset autosomal dominant Alzheimer disease.