Some authors included other AD-related markers, including acetylcholinesterase activity,20 Alz-50 immunoreactivity (a marker for tau)21 and the number of neurons that stained positive for the presence of tau.22 In each of these studies, the cognitively impaired schizophrenia group did not differ significantly from the normal control group and showed significantly lower levels of the AD pathology compared with an AD control group. Here, ACHE is linked to Alzheimer disease.