Bipolar disorder among an isolated island community in Ethiopia

Background: Psychiatric data on population groups of geographic and social isolates are rare, but can potentially give insights into factors of aetiological importance. The Zeway islanders have lived in geographic and cultural isolation for over three centuries. Aim: To determine the prevalence of major psychiatric disorders among the adult population of Zeway islands. Methods: A three stage screening design that included the use of structured interview instruments (CIDI and SCAN), key informants, and clinical assessment by psychiatrists was employed for case identification. Results: Prevalence of bipolar disorders among the adult population (n=1691) was 1.83% (n=31) with 66% of the cases originating from one of the islands that constitutes only 17.33% of the study population. Only one subject was identified with schizophrenia. Conclusions: A pattern of differential prevalence for bipolar disorders and schizophrenia appears to exist in this isolated population, which also seems shared by other isolated population groups. The high prevalence of bipolar disorders with clustering of cases on one island may represent an environmental or genetic factor of etiologic relevance that deserves further exploration.