APOE and psychotic disorder: We then created two strata for APOE status (by grouping carriers of one or two alleles together due to low numbers): no ε4 alleles (MBI‐psychosis, n = 160; No Psychosis, n = 1733) and one or two ε4 alleles (‘“ε4 carrier,” MBI‐psychosis, n = 91; No Psychosis, n = 766).