Introduction

Epidemiological research into schizophrenia aims to answer four essential questions.

1. What is the 'true' population frequency of the disorder in various populations and how is it distributed across the various groups within populations?

2. Do the incidence, manifestations, and course of schizophrenia vary in relation to factors of the physical and social environment?

3. Who is at risk and what forces determine or influence the risk of developing schizophrenia?

4. Can the answers to the above questions help explain what causes the disorder and how to prevent it?

The hallmark of the epidemiological method (see Chapter2.7) is the referral of any numerical findings about the occurrence of a disorder or its associated characteristics to a population base or denominator, such as person-years. The epidemiological study of a disorder usually proceeds from a description of its frequency and associations (establishing rates of occurrence) to testing hypotheses about risk and causes, using analysis of ratios between rates.

Schizophrenia has been studied extensively from an epidemiological perspective over the past hundred years. (1) Kraepelin, who introduced the concept of dementia praecox in 1896, anticipated the potential of the epidemiological method to 'throw light on the causes of mental disorder' and proposed comparative population studies of the psychoses and factors predisposing to them across different cultures.(2) In the first half of the twentieth century, epidemiological research into schizophrenia took two divergent paths. While European studies tended to have a strong focus on genetic risks, North American researchers investigated the social ecology of the disorder. A variety of techniques and study designs were explored and applied with considerable success by the pioneers of psychiatric epidemiology, and the contours of the epidemiological map of schizophrenia in Europe and North America were effectively laid down between the two World Wars. The early epidemiological studies were carried out by dedicated researchers who typically spent much of their time collecting data 'door to door' in small communities. Intimate knowledge of the respondents, access to multigenerational records from the local parish registers, and the co-operation of the community often resulted in studies that remain landmarks of psychiatric epidemiology (Table,!).

Table 1 Landmarks in the history of the epidemiology of psychoses: methods

During the last three decades, the scope of epidemiological studies of schizophrenia has expanded to include populations in Asia, Africa, and South America about which little had been known previously. The World Health Organization ( WHO) International Pilot Study of Schizophrenia and the subsequent WHO 10-country epidemiological study(l0ll> were the first systematic investigations of the comparative incidence, clinical manifestations, and course of schizophrenia in both developing and developed countries. The WHO programme provided an impetus for similar studies to be undertaken in India, China, the Caribbean, and Australia. Two major studies of psychiatric morbidity in the United States, the Epidemiological Catchment Area project and the National Comorbidity Survey, generated data on the prevalence of DSM-III/IIIR schizophrenia and related disorders in representative population samples. (1 ,.!3) Recent studies, initiated in the 1980s and 1990s, tend to make use of large existing databases such as cumulative case registers or birth cohorts to test hypotheses about risk factors in case-control designs, or include methods of genetic epidemiology within population-based studies. There is a tendency towards integrating epidemiological approaches with other types of aetiological research in schizophrenia/1.:4 This predicts an important role for epidemiology in the coming era of molecular biology of mental disorders.

Funny Wiring Autism

Funny Wiring Autism

Autism is a developmental disorder that manifests itself in early childhood and affects the functioning of the brain, primarily in the areas of social interaction and communication. Children with autism look like other children but do not play or behave like other children. They must struggle daily to cope and connect with the world around them.

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