Complex segregation analysis of schizophrenia in Santiago, Chile.

Genetic epidemiologic studies have provided evidence that genetic factors contribute to familial aggregation of schizophrenia. However, the precise mode of inheritance has not been elucidated. The majority of such studies have been carried out in Caucasian populations. The present study was performed in Santiago, Chile, whose population stems from the admixture of Amerindians with Spaniards. The sample consisted of 44 randomly ascertained schizophrenic probands (22 males and 22 females) with ages ranging between 20 and 48 years. The diagnosis was made according to DSM-III-R criteria. Both probands and relatives were interviewed using a structured interview (CIDI) and the DSM-III-R checklist. Complex segregation analysis was carried out using the computer program POINTER. The non-transmission model (Q = H = 0) was rejected as well as the recessive single locus (H = 0, Z = 1). The multifactorial, the single codominant, the non-major locus component, the non-polygenic component transmission model and the non-transmission of a major effect could not be rejected. The model that best fits the data of the present study is that of a mixed model with a great environmental component (93.12%). The frequency of the major gene was estimated at 0.000155. Our results are similar to previous reports in ethnically different populations.