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Title: Schizophrenia and affective psychosis in the North-East of Scotland : a case register study
Author: Powell, Anne
Awarding Body: University of Aberdeen
Current Institution: University of Aberdeen
Date of Award: 1975
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1. This thesis describes a statistical-genetical approach to the problem of aetiology in schizophrenia and affective psychosis. 2. The study can be seen to have three aims: (1) To establish population parameters for schizophrenia and affective psychosis specific to the North-East of Scotland; (2) To investigate the familial nature of schizophrenia and affective psychosis using linked family records; (3) To present a preliminary analysis of the heritability of liability to schizophrenia and affective psychosis, using the polygenic threshold model described by Falconer (1965). 3. The results of previous genetic studies of schizophrenia and affective psychosis are briefly outlined and critical consideration is given to a number of studies relevant to this investigation. 4. It is suggested that, on the basis of the results of previous studies, polygenic transmission is likely with respect to both schizophrenia and affective psychosis. 5. It is observed that there are sources of bias in some previous studies, as follows: (i) inappropriate population parameters, (ii) age corrections, and (iii) ascertainment of diagnoses. 6. Characteristics of the study area and its population are described. 7. The case register concept is explained and the principal features of the North-East Scottish psychiatric case register, from which data was derived for this study, are outlined. 8. Age and sex specific expectancy risks were derived for schizophrenia and affective psychosis in the North-East region of Scotland. 9. The method described is new to British studies and is based upon a Scandinavian study by Hagnell (1966). 10. Modifications were made to the method for the size of the population and the availability of data and these are described. 11. The cumulated lifetime expectancy risks for diagnosed cases of schizophrenia and affective psychosis, in the North-East of Scotland, are 1.9 per cent and 6.2 per cent respectively. 12. These estimates are higher than those previously reported by other British studies. 13. When the sexes are considered separately the overall risk is not very different - 1.8 per cent in males and 1.7 per cent in females for schizophrenia, and 5.8 per cent in males and 6.3 per cent in females for affective psychosis. 14. This finding is in contrast to earlier studies where a large excess of female affectives has generally been reported (e.g. Adelstein et al., 1968; Slater and Cowie, 1971) and a similar though smaller excess of males amongst schizophrenics (e.g. Adelstein et al., 1968). 15. The results suggested a possible reason for the changing sex ratio amongst affectives in an increase amongst males. 16. The expectancy risks also show that the elderly of both sexes still have a high risk of becoming schizophrenic or affective thus providing no support for the upper limits of the characteristic risk periods for schizophrenia and affective psychosis. 17. The expectancy risks and the annual incidence rates show no bimodality and therefore provide no support for separating early and late onset affective disorders into distinct genetic entities. 18. Some sources of bias affecting the population parameters of this study are outlined. 19. Reasons for the differences between the results of this and previous studies are suggested and discussed. 20. It is concluded that the sources of bias affecting the population parameters are unlikely to detract from their usefulness to planners, clinicians and researchers. The cumulated expectancy risks are an estimate of potential prevalence and are likely to be of use in forward planning. 21. An investigation of diagnostic resemblance amongst four types of relatives is described. The relatives are: husbands and wives, parents and children, siblings, and second degree blood relatives. 22. Significant concordance was found amongst married pairs with respect to schizophrenia and further investigation suggested that assortative mating might be of importance amongst schizophrenics. 23. Amongst blood relatives the diagnostic concordance was significant for both schizophrenia and affective psychosis. 24. Concordance was greater amongst first degree relatives than amongst those of the second degree type. 25. It is concluded that the results regarding diagnostic resemblance do not refute the importance of hereditary factors, neither are they felt to be inconsistent with polygenic inheritance. 26. Schizophrenia and affective psychosis were found to occur in significant numbers in the same families. 27. Whilst affective parents produced significant numbers of affective and schizophrenic offspring, schizophrenic parents produce only schizophrenic offspring. 28. A comparison of the consistency of diagnostic histories in mixed schizophrenia x affective families with that in concordant schizophrenic x schizophrenic and affective x affective families is described. 29. The results suggest that the presence of both disorders in the same family may qualitatively alter the symptoms of some members producing either atypical features or persons who manifest, at different times, the symptoms of both disorders. 30. Some deficiencies in the analysis are discussed and further research is suggested to clarify the relationship between schizophrenia and affective psychosis. 31. Using the method described by Falconer (1965), estimates of heritability of the liability to schizophrenia and affective psychosis were derived for two classes of relative: children and siblings. The heritability for schizophrenia was estimated to be 49 per cent ± 0.07 and 20 per cent ± 0.04 for children and siblings respectively. For affective psychosis the values were 19 per cent ± 0.05 for children, and -2 per cent ± 0.02 for siblings. 33. The estimated heritability values in his study are lower than those reported in previous studies. 34. It is pointed out that the present study is rather different from previous studies in the source of data and the methodology; much of the discrepancy between this study and previous studies can be attributed to these differences. 35. The genetic correlation in liability (Falconer, 1960) was used to determine whether a genetic associction exists between schizophrenia and affective psychosis. 36. A value, for the genetic correlation, of + 0.26 was obtained which was inconclusive in suggesting a genetic association. 37. In the light of the genetic analysis it is suggested that modifications are necessary to render psychiatric case register data more suitable for further genetic study, and some recommendations are made.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available