MAPT and schizophrenia: Decreases in CSF concentrations of amyloid-beta 42 (Aβ42) and elevations in total tau and phosphorylated tau are used as biomarkers for AD.23 Two studies that measured CSF Aβ42 levels found significantly lower levels of Aβ42 in patients with schizophrenia compared with normal controls (online supplemental table 1).