We link schizophrenia in families from the genetically isolated South African Afrikaner population to
chromosome 13q (n =51), 1p (n =23) and combined 13q & 1p (n =18). Patients with linkages to chromosome
13q were 4.16 times more likely to meet diagnostic criteria for schizoaffective disorder compared to patients
with linkage to 1p. A third of patients with linkage to both 13q & 1p met diagnostic criteria for SAD. There was a
significant positive relationship between suicidality and a diagnosis of schizoaffective disorder. Identifying
linkage to chromosome 13q may be informative in identifying suicide risk early and prevent morbidity and
mortality in schizophrenia patients.