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The increased risk of psychosis in African-Caribbean migrants to the UK: A replication
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developed a mathematical model which purported to show that an age-incidence effect could account for previous season-ofbirth findings. We show that, in fact, his own model predicts that there is an ever declining age-incidence effect which soon becomes negligible with time and that, in any case, the arbitrary parameters chosen maximise the age-incidence effect. We show that his model for the instantaneous incidence is wrong and replace it with a more realistic model. We then develop predictions of the actual magnitude of the age-incidence effect and demonstrate that it is negligible with time.
II.C. Immigration IIC. 1 THE INCREASED RISK OF PSYCHOSIS IN AFRICAN-CARIBBEAN MIGRANTS TO THE UK: A REPLICATION G. Harrison, J. Brewin, R. Cantwell, T. Dalkin, R. Fox, I. Medley a n d C. Walder
liB. 5 WINTER BIRTH EXCESS IN SCHIZOPHRENICS BORN IN FRENCH URBAN
AREAS
H. Verdoux 1, N. Takei 2, R. Cassou de Saint M a t h u r i n 1, R. M u r r a y 2 a n d M. Bourgeois I
IIPSO, Department of Psychiatry, University of Bordeaux II, Centre Carreire, 121 rue de la Bbchade, 33076 Bordeaux Cedex, France 2Department of Psychological Medicine, Institute of Psychiatry and King's College Hospital, De Crespigny Park, London SE5 8AF, UK Previous studies have suggested that winter birth in urban areas might be associated with an increased risk of schizophrenia. Survey questionnaires were mailed to all French public departments of adult psychiatry (excluding those of the region of Paris) to collect data on patients with a hospital diagnosis of schizophrenia. Data were obtained for 4139 schizophrenic patients born in France. Place of birth was defined according to the administrative subdivision of French metropolitan territory into 95 'd~partements'. Demographic data provided by successive censuses were used to assess density of population in those 'd6partments' for each decade of this century. The distribution of density measure in the sample of patients was initially categorised into quartiles, but the first three quartiles were grouped together since only those allocated to the highest quartile (i.e., birth in the most densely populated areas) showed a distinct winter-birth (January-March) excess. After adjustment for gender and period of birth, a 20% increase (OR 1.20, 95% CI 1.03 1.40, p=0.02) of winter births was found among patients born in highly densely populated areas (>136 inhabitants/km2) compared to those born in other areas. These results suggest that seasonal early environmental risk factor(s) predominantly operate in urban areas, and are linked to schizophrenia.
Academic Department of Psychiatry, Professional Unit, Mapperley Hospital, Porchester R + oad, Nottingham, NG3 6AA, UK Several studies have replicated the finding by Harrison et al. +(1988) of increased incidence of schizophrenia and related psychoses in first and second generation migrants from the Caribbean. Incidence ratios of between 3 and 6 have been reported. Most studies satisfy methodological objections based upon potential error in case definition but there is concern about indirect methods of calculating the population at risk. A further prospective study was therefore undertaken in Nottingham assembling an inception cohort of psychotic patients (n= 169) presenting from a defined catchment area. The denominator was derived from the 1991 census which included ethnic origin. Correction factors were applied for potential under-enumeration of risk groups. Caseascertainment was based upon all service contacts and followed by in-depth assessments including the SCAN and collateral history from informants. Patients of African Caribbean ethnicity had substantially increased age-specific rates (incidence ratios above 5) for all psychotic disorders including schizophrenia, particularly in second generation (UK born) and in males. The size of the increase and methodological safeguards employed support the validity of this consistently replicated finding. A migration history (extending to the second generation) is a significant risk factor for psychoses in certain populations and justifies systematic evaluation of possible etiologies.
IIC. 2 THERE IS A HIGHER MORBID RISK OF SCHIZOPHRENIA IN THE SIBLINGS OF 2ND GENERATION CARIBBEAN SCHIZOPHRENIC PROBANDS COMPARED TO WHITE COUNTERPARTS G. H u t c h i n s o n , N. Takei, T. Fahy, D. Bhugra, P. M o r a n a n d R.M. M u r r a y
Genetics Section, Dept of Psychological Medicine, Institute of Psychiatry, London SE5 8AF, UK There has been much speculation about the reason for the high rates of schizophrenia among the Caribbean popula-
developed a mathematical model which purported to show that an age-incidence effect could account for previous season-ofbirth findings. We show that, in fact, his own model predicts that there is an ever declining age-incidence effect which soon becomes negligible with time and that, in any case, the arbitrary parameters chosen maximise the age-incidence effect. We show that his model for the instantaneous incidence is wrong and replace it with a more realistic model. We then develop predictions of the actual magnitude of the age-incidence effect and demonstrate that it is negligible with time.
II.C. Immigration IIC. 1 THE INCREASED RISK OF PSYCHOSIS IN AFRICAN-CARIBBEAN MIGRANTS TO THE UK: A REPLICATION G. Harrison, J. Brewin, R. Cantwell, T. Dalkin, R. Fox, I. Medley a n d C. Walder
liB. 5 WINTER BIRTH EXCESS IN SCHIZOPHRENICS BORN IN FRENCH URBAN
AREAS
H. Verdoux 1, N. Takei 2, R. Cassou de Saint M a t h u r i n 1, R. M u r r a y 2 a n d M. Bourgeois I
IIPSO, Department of Psychiatry, University of Bordeaux II, Centre Carreire, 121 rue de la Bbchade, 33076 Bordeaux Cedex, France 2Department of Psychological Medicine, Institute of Psychiatry and King's College Hospital, De Crespigny Park, London SE5 8AF, UK Previous studies have suggested that winter birth in urban areas might be associated with an increased risk of schizophrenia. Survey questionnaires were mailed to all French public departments of adult psychiatry (excluding those of the region of Paris) to collect data on patients with a hospital diagnosis of schizophrenia. Data were obtained for 4139 schizophrenic patients born in France. Place of birth was defined according to the administrative subdivision of French metropolitan territory into 95 'd~partements'. Demographic data provided by successive censuses were used to assess density of population in those 'd6partments' for each decade of this century. The distribution of density measure in the sample of patients was initially categorised into quartiles, but the first three quartiles were grouped together since only those allocated to the highest quartile (i.e., birth in the most densely populated areas) showed a distinct winter-birth (January-March) excess. After adjustment for gender and period of birth, a 20% increase (OR 1.20, 95% CI 1.03 1.40, p=0.02) of winter births was found among patients born in highly densely populated areas (>136 inhabitants/km2) compared to those born in other areas. These results suggest that seasonal early environmental risk factor(s) predominantly operate in urban areas, and are linked to schizophrenia.
Academic Department of Psychiatry, Professional Unit, Mapperley Hospital, Porchester R + oad, Nottingham, NG3 6AA, UK Several studies have replicated the finding by Harrison et al. +(1988) of increased incidence of schizophrenia and related psychoses in first and second generation migrants from the Caribbean. Incidence ratios of between 3 and 6 have been reported. Most studies satisfy methodological objections based upon potential error in case definition but there is concern about indirect methods of calculating the population at risk. A further prospective study was therefore undertaken in Nottingham assembling an inception cohort of psychotic patients (n= 169) presenting from a defined catchment area. The denominator was derived from the 1991 census which included ethnic origin. Correction factors were applied for potential under-enumeration of risk groups. Caseascertainment was based upon all service contacts and followed by in-depth assessments including the SCAN and collateral history from informants. Patients of African Caribbean ethnicity had substantially increased age-specific rates (incidence ratios above 5) for all psychotic disorders including schizophrenia, particularly in second generation (UK born) and in males. The size of the increase and methodological safeguards employed support the validity of this consistently replicated finding. A migration history (extending to the second generation) is a significant risk factor for psychoses in certain populations and justifies systematic evaluation of possible etiologies.
IIC. 2 THERE IS A HIGHER MORBID RISK OF SCHIZOPHRENIA IN THE SIBLINGS OF 2ND GENERATION CARIBBEAN SCHIZOPHRENIC PROBANDS COMPARED TO WHITE COUNTERPARTS G. H u t c h i n s o n , N. Takei, T. Fahy, D. Bhugra, P. M o r a n a n d R.M. M u r r a y
Genetics Section, Dept of Psychological Medicine, Institute of Psychiatry, London SE5 8AF, UK There has been much speculation about the reason for the high rates of schizophrenia among the Caribbean popula-