title: Rates of treated schizophrenia and its clinical and cultural features in the population isolate of the Iban of Sarawak: a tri-diagnostic approach.
abstract: BACKGROUND
  We present results of a study of treated rates of schizophrenia among the Iban of Sarawak, Malaysia. Most Iban live in longhouses, each comprising a kindred group of up to 300 individuals. Cultural practices such as minimal intermarriage with members of adjacent ethnic groups and in-depth genealogical knowledge make them a population suitable for genetic investigation. Iban culture is conducive to a focus on symptoms and illness, and to patterns of treatment-seeking behaviour that are enthusiastic and persistent.
  
  
  METHODS
  We identified all known cases of psychotic disorder within a defined catchment area based on an exhaustive survey of available medical records. From corresponding Malaysian census data (91,056 persons), we report rates of treated schizophrenia in the Iban population, using three diagnostic systems, as well as the demographic and clinical characteristics of these individuals.
  
  
  RESULTS
  The most frequent presenting complaints were insomnia and aggression. We found higher treated rates for narrowly defined schizophrenia among males, but no significant gender difference for age of onset. Estimates of treated rates to age 55 years (per 10,000) for narrow schizophrenia were 41.9 (ICD-10), 56.5 (DSM-IV), and 83 (RDC), while the rates for broad schizophrenia were 105.5, 103.2, and 107.5 respectively.
  
  
  CONCLUSIONS
  Treated rates of schizophrenia were higher than the reported prevalence for many populations at risk, including many small-scale societies, although different methodological approaches may partly explain these findings. Given the cultural patterns of Iban treatment-seeking behaviour, treated rates of schizophrenia reported here may closely approximate the population prevalence of this disorder.
authors.affiliation: University of Adelaide, Department of Psychiatry, L4 Eleanor Harrald Building, Royal Adelaide Hospital, Adelaide, SA 5000, Australia.
authors.forename: Robert
authors.initials: R
authors.lastname: Barrett
authors.forename: Peter
authors.initials: P
authors.lastname: Loa
authors.forename: Edward
authors.initials: E
authors.lastname: Jerah
authors.forename: Derek
authors.initials: D
authors.lastname: Nancarrow
authors.forename: David
authors.initials: D
authors.lastname: Chant
authors.forename: Bryan
authors.initials: B
authors.lastname: Mowry
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000374:Aggression; D003466:Cultural Characteristics; D003710:Demography; D016021:Epidemiologic Studies; D005006:Ethnicity; D005260:Female; D006801:Humans; D008296:Malaysia / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D012307:Risk Factors; D012559:Schizophrenia / Q000150:complications / Q000453:epidemiology* / Q000628:therapy*; D012737:Sex Factors; D007319:Sleep Initiation and Maintenance Disorders; D012944:Social Support