Is it necessary to distinguish between first and second generation African-Caribbean populaton in psychiatric research?

In attempting to identify factors responsible for the onset, course and prognosis of an illness, it is necessary to identify differences between generations in order to separate the effects of heritability and environment. Ethnicity and culture can also be examined in this way so that changes in culture occasioned by changes in environment can be assessed in terms of their impact on illness. In our work on the family history of psychoses among the African-Caribbean population in Britain we have found that for schrizophrenia, the relatives of first generation (those born in the Caribbean) and white psychotic patients share similiar risks while the risk is markedly increase in the relatives, particularly siblings of the second generation (those born in Britain to Caribbean parents) psychotic patients. For affective psychoses, we have found that the risk in the relatives of the first generation patients is significantly less than for both the white and the second generation relatives. These differences would have been much less noticeable if the separation between first and second generation patients had not been undertaken and would have been more difficult to interpret. Our findings do suggest that there are factors acting on the second generation making them more susceptible than their first generation counterparts to psychotic illness. This therefore diminishes the likelihood that the increased risk of illness in the second generation is due to a genetic effect and is much more likely to be mediated by some selective environmental effects acting either specifically on those families already afflicted by the disease or more generally on the entire second generation population.(AU)

A study of the ethnicity and the aetiology of schizophrenia - background and objectives

High rates of schizophrenia have been repeatedly reported among the African-Caribbean population in Britain. There has been no satisfactory explanation for these increased rates and while migrants in general are thought to be at increased risk, the incidence of schizophrenia is especially raised among African-Caribbean population that was born in Britain (second generation). Preliminary data from the Caribbean also suggest that there is a specific pathological process occuring in Britain. The available evidence in Britain also suggest that there are environmental factors which are selectively affecting the African-Caribbean population in Britain that are making them more vulnerable to schizophrenia. The study of high risk groups can be very instrumental in the elucidation of the aetiology of disease and therefore the study of this population may shed light on the aetiology of schizophrenia as a whole. In addition, this increased incidence of schizopherenia places a heavy demand both on the families of an already disadvantaged group as well as on the psychiatric services, particularly in the inner cities where the majority of African Caribbean people live in Britain. An understanding of the determinants of this increased risk of schizophrenia would lead to appropriate intervention strategies especially in the areas of prevention and provision of effective care. The study will be a population based case control study of the first contact schizophrenia in African-Caribbeans and the remaining population in three British centres. The research hypotheses are that the African-Caribbeans psychotic patients will show more evidence of risk increasing social factors, in particular adverse life events and a marked discrepancy between expectations and achievement. Their siblings will also show a high risk for psychosis suggesting that certain families are more susceptible to the social adversity associated with migration. The study will combine two strategies; the first to determine the absolute risk of the disorder, and the other to identify the risk factors which mediate the onset and course of the illness. We will also carry out a one year outcome study to examine the needs for mental health care in the African-Caribbean population and the extent to which treatment is appropriate.(AU)