First-contact incidence rates of schizophrenia in Trinidad and one-year follow-up.

BACKGROUND: Incidence rates of schizophrenia among UK African-Caribbeans have been reported as high. Various explanations including selective migration and genetic vulnerability have been proposed. METHOD: In one calendar year, all new cases of psychosis presenting to various psychiatric services in two clearly defined geographical catchment areas in Trinidad-one in the rural south and the other an urban area-were studied. Standardised diagnostic instruments were applied and information collected using WHO screening and measurement instruments. RESULTS: A total of 56 cases were collected, giving an incidence rate of 2.2/1000 of broad schizophrenia with a rate of 1.6 for S+ schizophrenia. CONCLUSION: These rates are similar to those from the WHO study in Honolulu and Aarhus, and much lower than the rates for African-Caribbeans in London. The cases were followed up for one year and the poor outcome rate for schizophrenia was 19%. The findings are discussed in a cross-cultural context and suggestions for future research made.

The incidence of mania: time trends in relation to gender and ethnicity.

In order to investigate conflicting reports about possible changes in the incidence of mania, we established first contact rates for mania in the defined area of Camberwell between 1965 and 1984. There was some evidence for an increase in the first contact rate of mania, especially in females. This rise may be associated with the influx into Camberwell of individuals of Afro-Caribbean origin who showed significantly higher rates than the white group [adjusted rate ratio 3.1; 95% confidence interval (CI) 1.4-6.9] and more often displayed mixed manic and schizophrenic symptomatology (risk ratio 2.2; 95% CI 1.1-4.3). We conclude that the incidence of mania has not decreased and may actually have increased. High rates of mental illness among members of ethnic minorities are not specific to schizophrenia, suggesting that a risk factor common to both manic and schizophrenic illness is more prevalent among these groups.

Schizophrenia and Afro-Caribbeans. A case-control study.

A case-control study was performed using 90% of all first-contact patients with a clinical diagnosis of schizophrenia residing in the London borough of Camberwell between 1965 and 1984. Cases and controls were obtained from the Camberwell psychiatric case register. Controls were those presenting with first episodes of non-psychotic disorders, matched for age, sex and period. The risk of schizophrenia was greater in those of Afro-Caribbean ethnicity, irrespective of age, gender or place of birth. This risk increased over the study period. The results cannot be explained by changes in the age, gender or ethnic structure of the local population. Effects of misdiagnosis or change in diagnostic practice were reduced by using uniform operational criteria. Possible explanations include maternal exposure to unfamiliar infective agents, a differential fall in the age at onset of illness, or worsening social adversity.