Psychosis In The Inner City

The Camberwell First Episode Study

DAVID J CASTLE, DAVID J CASTLE, Perth; et al. David J. Castle University of Western Australia

• Publisher: Psychology Press
• Year: 2013
• Topic: Psychology
• eBook ISBN:
  9781134837410
• Subtopic: History & Theory in Psychology
• Index: Psychology

The "epigenetic puzzle" which is schizophrenia, forms the focus of this Monograph, But The Authors Do Not Sit Comfortably With The Notion That this is an entity. Rather, they approach the non-affective psychoses on a broad epidemiological base, ascertaining cases of so-called "functional" psychoses over a quarter of a century. They examine admission policies, showing that patients are admitted to hospital on the grounds of their particular presentation, rather than their diagnosis. They explore Differences Between Males And Females With Psychotic Disorders, And Show that gender is a more powerful influence than diagnosis. They investigate trends over time, and find that demography is the major influence. Looking at criminality, they show that the factors predicting criminal Behaviour In Individuals With Psychotic Illness Are Much The Same In those without psychotic illness. And they trace the longitudinal course of illness, putting paid to the schizophrenia/manic depression dichotomy.; This monograph is an overview of the ideas and many of the findings generated by a highly productive group of researchers. It has a good chance to become one of the standard references in several of the key aspects of schizophrenia.

Chapter One

Schizophrenia: The Epidemiology of a Provisional Category

This book takes the epidemiology of schizophrenia as its central theme, and focuses particularly on the way in which the disorder presents in a large city, namely London. This focus is timely because both the incidence and prevalence of the disorder are higher in large cities (Freeman, 1994), and the care (or lack of care) of psychotic patients in large cities such as London is giving rise to considerable public concern. Furthermore, there is increasing evidence that being born or brought up in an urban environment appears to increase the risk of schizophrenia (Lewis, David, Andréason,&Allebeck, 1992; Castle, Scott, Wessely,&Murray 1993).

Our research addresses such questions as whether the incidence of the disorder is changing, and which groups are at particular risk. But more than that, it uses epidemiological techniques to ask whether schizophrenia can be subdivided into more meaningful subgroups and why it appears different in men and women and in those with onset in early or late adult life. The justification for the study is that an understanding of the epidemiology of schizophrenia will not only help us to plan the facilities necessary for its optimum treatment but may also help us to find the causes of the disorder.

In this introduction, we will discuss four matters: first, general principles concerning variations in the incidence of disease and what we can learn from them; second, the advantages and disadvantages of case register studies; third, the validity of the concept of schizophrenia; and finally, the implications of risk factor research for the epidemiological studies reported in this monograph.

Variations in Incidence of Disease in Time, Place and Person

The description of the variation in incidence of disease in different times, places, and groups of persons is the basic epidemiological challenge for relatively common disorders such as schizophrenia. Variation in disease incidence can provide important clues as to the role of environmental and/or genetic factors in bringing on the disease (Khoury, Beatty,&Cohen, 1993; see Table 1.1)

Table 1.1
Aetiological Implications Of Variation In Disease Occurrence In Different Settings

	Indicating the presence of:
Epidemiological setting	Genetic factors	Environmental factors
Temporal variation	–	+
Spatial variation	(+)	+
Ethnic variation	+	+
Gender differences	+	+
Social class variation	–	+

Socioeconomic status. Social class variation in disease occurrence can provide evidence for differential exposure to environmental factors (Susser&Susser, 1987). Unfortunately, it may be difficult to identify what these factors actually are, due to the large overlap between the various factors that make up “social class”, such as lifestyle, nutrition, employment, and place of residence. Of course, the fact that social class variation in disease occurrence points towards the role of environmental factors does not exclude the possibility that genetic factors confer a particular susceptibility to environmental factors (genotype–environment interaction), nor that genetic risk factors for disease play a role in social segregation (Eaton, 1980).

Geographic variation. Although geographic variation in gene frequencies for a variety of traits has been established (e.g. Sokal, 1988; Sokal, Harding,&Oden, 1989), in some instances of spacial variation, genetic factors are unlikely to play a direct role. For example, the best known example of spatial variation in the incidence of schizophrenia within countries is that associated with urban residence. It is unlikely that, within one and the same country, the genetic make-up of individuals living in urban areas is markedly different from that of those living in rural areas. Furthermore, for multifactorial disorders such as psychosis, with no simple one-to-one relationship between genotype and phenotype, the prevalence of disorder in urban areas would need to be many times higher than in rural areas, to confound, through genetic mechanisms, any relationship between disease incidence and urbanicity. A previous investigation has shown that this is unlikely to be the case (Lewis et al., 1992).

Therefore, geographic variation in the incidence of schizophrenia has often been interpreted as evidence for variation in environmental risk factors. Indeed, Kety (1980) has linked it to variation in risk factors associated with both urbanicity and social class by stating: “To the extent that perinatal injuries, malnutrition and infection may play a role in the environmental etiologies of schizophrenia, their impact would be exaggerated in the lower social classes in large cities.” Since this monograph deals with the predominantly working-class population of Camberwell, we hope to be able to address some of these issues.

Migrant groups. The study of variation in incidence in migrant groups and their offspring can also shed light on the relative role of environmental and genetic factors. For example, if the disease in question is mostly genetically determined, disease frequency in migrant groups will closely resemble the frequency of disease in the country of origin. A similar pattern might, of course, be seen if a premigration, childhood environmental exposure in the country of origin, or an environmental exposure in the cultural “micro-environment” of the migrant family in the host country, is strongly associated with later development of disease. In the latter case, one would expect that successive generations of descendants of the migrants would show a progressively lower risk of illness. On the other hand, if environmental factors operating later in life exert a strong influence, the disease frequency in migrant groups may be expected to resemble more closely the disease frequency among individuals in the host country.

If the disease frequency in the migrant groups exceeds both that in the country of origin and the host country, then this may be an indication that the risk of the disorder is being increased either by specific factors associated with being a migrant in the host country, or by particular characteristics of the migrants, setting them apart from individuals in the host country (selective migration).

In practice, the results of migrant studies are often inconclusive. As already mentioned, migrants may be highly unrepresentative in relation to the source population, and migration status is often confounded by a host of factors including demographic characteristics, education, religion, health status, drug use, diet, access to health care, and influence of cultural pathoplastic factors on disease presentation. Furthermore, estimates of disease rates in the country of origin may be unreliable because of differences in availability of health care facilities and/or the quality of census information. Finally, migrant and ethnic groups often are difficult to define for the purposes of scientific research (McKenzie&Crowcroft, 1994), and even if they can be reliably delineated, it must be kept in mind that such groups are dynamic and undergoing continual change.

The issue of ethnic group and risk of schizophrenia is taken up in Chapters 8, 9, and 10 in which studies designed to overcome the above methodological difficulties are presented.

Gender differences. Gender-related variation in incidence has been demonstrated for many diseases such as lung cancer and coronary heart disease (more frequent in men), and autoimmune disorders (more frequent in women). Such differences sometimes provide straightforward information. For example, higher prevalence of smoking in men is likely to contribute significantly to the difference in lung cancer incidence in men and women, while the rising number of women smoking over the last decades provides a plausible explanation for the recent narrowing of this gender gap. Similarly, although the great majority of the genome in men and women is shared, simple recessive X-linked disorders occur more frequently in men because women are conferred relative protection by the presence of a second X chromosome. In general, however, the demonstration of a gender difference is only the initial step in trying to unravel the role of a host of possible genetic, social, environmental, hormonal, and occupational factors and their potential interactions.

The study of gender differences in schizophrenia has been very productive, but here also the interpretation of the findings is not straightforward. These issues will be discussed in detail in Chapters 4 and 5.

Temporal trends. Temporal trends in disease incidence in large populations are unlikely to be associated with changes in the frequency of contributing genes, and therefore point to changes in exposure to environmental risk factors. For example, in Western countries the rise in ischaemic heart disease following the 1940s is thought to have arisen from changes in the diet, while the change in incidence of poliomyelitis appears to be related to changes in exposure to protective factors (Barker, 1989).

It is very difficult, however, to show accurately trends in disease incidence, as the data used to measure disease incidence usually rely on health-care statistics, which are affected by changing diagnostic concepts and changing service provisions over time; thus, they cannot be relied on to reflect the true incidence of the disorder under study. One way of attempting to obtain more accurate information about possible temporal trends in schizophrenia and related disorders is to use data from a case register, with systematic ascertainment of cases.

The Role of Case Register Studies

There has been a considerable vogue in recent years for studies of schizophrenia at first onset (Lieberman et al., 1993; McGorry, Edwards, Mihalopoulos, Harrigan,&Jackson, 1996). Although an advance on studies of mixed populations of patients admitted to hospital at various points in the evolution of their illnesses, such first admission studies suffer two major disadvantages. First, they often concern admissions only, and as will be demonstrated in Chapter 3, a proportion of such individuals are not admitted during their first onset. Second, such studies do not generally draw their patients from a defined catchment area; therefore they are subject to biases in referral patterns and cannot be said to be representative of all first onset cases of schizophrenia. We have attempted to avoid these problems by using a mental health case register to identify a sample comprising of all cases of schizophrenia and related psychotic illnesses from the defined area of Camberwell in southeast London at the point of their first presentation to the psychiatric services.

Because of the various “filters” operating between the decision to seek help for mental health problems and help from specialised services (Goldberg&Huxley, 1980), only a minority of all patients with mental health disorders in a geographical area will ever be registered by a mental health case register. Most individuals deciding to seek help for “minor” mental health problems will be treated by their general practitioner. Therefore, treated incidence as measured by case register contacts will not be an accurate reflection of the total morbidity. However, disorders such as schizophrenia will result in contact with mental health services in the great majority of cases (Bamrah, Freeman,&Goldberg, 1991; Cooper et al., 1987), and the treated incidence will be more an approximation of the true incidence, especially if both community and in-patient contacts are registered (Goldacre, Shiwatch,&Yeates, 1994).

In calculating treated incidence of a disorder, diagnosis at first admission may be used, but diagnostic change can occur. It has been estimated, for example, that the incidence using first admission diagnosis is only half the incidence using diagnosis of schizophrenia ever recorded in the patient’s career (Goldacre et al., 1994). Bias may occur if clinicians are differentially reluctant to apply a first diagnosis of schizophrenia with some groups, for example certain ethnic groups. This issue will be further examined in Chapters 8 and 9.

The strength of a case register lies in its epidemiological properties: (1) it covers a well-circumscribed geographical area with a well-defined population at risk; (2) it systematically registers all cases within that area who are referred for mental health treatment; (3) it registers the same data for all individuals in a standardised way. The drawbacks are that (1) data such as diagnosis and details on previous treatment are gathered in a clinical setting, which limits their reliability; (2) pathways to mental health care may differ as a function of diagnosis and other important characteristics; (3) it can only collect a minimum number of relevant variables at the expense of information on possible confounders.

The first drawback can be overcome, by including systematic checks using another source of information, such as case records (see Chapter 2). However, the second drawback cannot usually be overcome in a simple way, as pathways into care can only be established through detailed studies. Similarly, it may be difficult to obtain information on possible confounders. Case register data should therefore be used to address issues that are not entirely dependent on pathways into care and not likely to be confounded by third variables about which no information is available. Having said this, studies suggest that, in a country like England, most patients with schizophrenia do make contact with the psychiatric services in the early stages of their illness (e.g. Cooper et al., 1972).

The Validity of the Concept of Schizophrenia

Any researcher carrying out a study such as ours is immediately confronted by the questions of diagnosis and definition of schizophrenia. The answers to these questions are far from simple. From the late 1960s onwards, psychiatrists spent much effort on improving the reliability of psychiatric diagnosis in general, and that for schizophrenia in particular (American Psychiatric Association, 1994; Cooper et al., 1972: Spitzer, Endicott,&Robins, 1978; Wing, Cooper&Sartorius, 1974). The result has been the development of a series of operational definitions of schizophrenia which have acceptable diagnostic reliability but, as will be seen throughout this monograph, considerable doubt as to which should be adopted. The basic problem is that we do not know whether the concept of schizophrenia has any validity, and even if it has, which operational definition best reflects that validity (Brockington, Kendell,&Leff, 1978; Crow, 1985; Murray, Lewis,&Reveley, 1985).

Part of this controversy centres on the relative merits of a narrow definition (e.g. DSM-IV; APA, 1994) or a broad definition (e.g. as in the PSE/CATEGO system; Wing et al., 1974). This in turn arises from uncertainty concerning the boundaries of the condition, and in particular over whether...

Table of contents

• Cover
• Half Title
• Title Page
• Copyright
• Contents
• Acknowledgements
• Preface
• Abstract
• 1. Schizophrenia: The epidemiology of a provisional category
• 2. Methods for the 1965–1984 study
• 3. Diagnostic issues and admission policies
• 4. The effect of gender on age at onset of psychosis
• 5. Subtypes of schizophrenia as expressions of wider dimensions of psychosis
• 6. Late onset schizophrenia
• 7. Crime and schizophrenia in Camberwell
• 8. Trends in the incidence of the functional psychoses
• 9. A case control study of ethnicity and schizophrenia
• 10. Psychotic illness in ethnic minorities: Evidence from the 1991 UK Census
• 11. The longitudinal perspective: The Camberwell collaborative psychosis study
• 12. Summary and conclusions
• References
• Glossary
• Appendix 1a
• Appenxix 1b
• Appendix 1c
• Appendix 1d
• Appendix 2
• Author Index
• Subject Index