Epidemiology of first-episode psychosis: illustrating the challenges across diagnostic boundaries through the Cavan-Monaghan study at 8 years.

The epidemiology of first-episode psychosis is poorly understood because of the paucity of systematic studies, yet it constitutes the fundamental basis for understanding the disorder and the foundations on which clinical, biological, therapeutic, and long-term outcome studies are built. A particular need is to clarify the diagnostic breadth of first-episode psychosis and, on this basis, to undertake systematic comparisons across representative populations of the psychoses, to include comparisons with first-episode mania. Considered here is the new generation of prospective studies that may be able to inform in some way on these issues. Attainment of the above goals requires prolonged accrual of "all" cases of nonaffective, affective, and any other psychotic illness, including first-episode mania, to derive the required representative populations. To illustrate some of the challenges, the structure of the Cavan-Monaghan prospective first episode study is described and its interim findings are outlined, as rural Ireland provides psychiatric care based on strict catchment areas and is characterized by substantive ethnic and socioeconomic homogeneity and stability. It is argued that there are 3 primary diagnostic nodes (schizophrenia spectrum psychosis, bipolar disorder, and major depressive disorder with psychotic features) around which there exist numerous additional, overlapping, and well-populated diagnostic categories that are distinct only in terms of their operational definition. Only through systematic, epidemiologically based studies that access this intrinsic diversity are we likely to understand fully the origins and pathobiology of first-episode psychosis.

Schizophrenia, schizoaffective and bipolar disorder within an epidemiologically complete, homogeneous population in rural Ireland: small area variation in rate.

While a controversy has endured as to whether schizophrenia evidences the geographical variations in rate that characterise essentially all medical conditions, even less is known of such fundamental aspects of the epidemiology of schizoaffective and bipolar disorder. Within an ethnically and socioeconomically homogeneous region of rural Ireland, population 29,542, several methodological refinements were adopted to seek an epidemiologically complete population of 'all' cases of these disorders, with each potential case interviewed and diagnosed. Prevalence and morbid risk were calculated over the region as a whole and for each of the 39 constituent District Electoral Divisions [DEDs], by place at birth and by place at onset. Using multiple sources of information, 115 cases of schizophrenia, 33 of schizoaffective disorder and 77 of bipolar disorder were identified. Unremarkable overall prevalence and morbid risk values obscured marked variation between District Electoral Divisions for schizophrenia. No such variation was observed for bipolar disorder. These data indicate, using improved methodology, that what is often interpreted as an invariant overall rate of schizophrenia across countries and cultures may not apply to spatial microstructure; macroscopic rates can obscure small area variations when ethnic and socioeconomic diversity are minimised and effects of urbanicity are absent. Under these conditions, small area variations in bipolar disorder may be limited.

Prospective analysis of premature mortality in schizophrenia in relation to health service engagement: a 7.5-year study within an epidemiologically complete, homogeneous population in rural Ireland.

While premature death in schizophrenia is well recognised, mortality risk has received little longitudinal study in relation to population representativeness and patient engagement with health services. Within a rural Irish catchment area of socioeconomic, ethnic and geographical homogeneity and low residential mobility, an epidemiologically complete population of 72 patients with schizophrenia was followed up over 7.5 years in order to quantify mortality prospectively. Information was obtained in relation to 99% of the cohort, with 94% of those surviving retained in engagement with psychiatric care. There were 25 deaths (35% of cohort). A relative risk of 2.06 (95% CI, 1.40-2.80; P < 0.001) among this epidemiologically complete population may constitute an estimate of risk for mortality inherent to schizophrenia when disengagement from health services, residential mobility and socioeconomic, ethnic and geographical diversity are minimised. On long-term prospective evaluation, risk for death in schizophrenia was doubled on a background of enduring engagement in psychiatric care with increasing provision of community-based services and introduction of second-generation antipsychotics.

First-episode schizophrenia, bipolar disorder and other psychoses in a rural Irish catchment area: incidence and gender in the Cavan-Monaghan study at 5 years.

BACKGROUND: The potential of first-episode studies in schizophrenia is maximised through systematic epidemiological, clinical and biological comparisons between homogeneous populations of the psychoses. AIMS: To conduct prolonged accrual of 'all' cases of non-affective and affective psychotic illness on an epidemiologically complete basis. METHOD: Within the region covered by Cavan-Monaghan psychiatric service (population 102,810), all putative cases of first-episode psychosis were diagnosed using DSM-IV. RESULTS: From 1995 to 2000, 69 cases of psychosis were ascertained, the incidence being 2.3-fold lower in females than in males. On resolving the 'core' diagnoses of schizophrenia and bipolar disorder, incidence of schizophrenia among women was 7.5-fold lower than among men whereas incidence of bipolar disorder among women was 6.6-fold lower than among men. CONCLUSIONS: This homogeneous population, which eliminates factors associated with urbanicity and minimises confounding factors such as socioeconomic, ethnic and geographical diversity, shows a markedly reduced incidence among females both of schizophrenia and of bipolar disorder.