PhD Students

Background: Schizophrenia (Dementia Praecox) and bipolar disorder (manic depression) are the main classes of mental disorder distinguished within the major functional psychoses. Irish psychiatric services (1998) identified bipolar disorder as having the highest (271.4 per 100,000) and schizophrenia the third highest (172.6 per 100,000) admissions rate to psychiatric hospitals and units throughout Ireland. Such widespread debilitating illnesses represent a real social and economic problem to Irish society and thus, credit further investigation.

No unequivocal scientific evidence for any single aetiological factor has been identified for either schizophrenia or bipolar disorder. Although a genetic component has been clearly established for these disorders an extensive body of literature suggests that environmental factors play important etiological roles, as environment drives gene expression. Two basic types of environmental risk factors have been implicated- biological factors at time of birth and social/environmental factors operating at time of onset. The latter pose greater importance for the present project as it involves a social dimension incorporating such aspects as social isolation, social class, socio-economic status, occupation and education and a physical dimension involving such factors as, the hydrological system, the biochemistry of the soil and the underlying geology of the area.

Study Hypothesis: If the risk of developing these psychiatric illnesses is influenced by an environmental factor then the distribution of prevalence rates maybe geographically uneven, reflecting the spatial distribution of the relevant causal factor(s).

Aim: The principal aim of this project is to assess whether the spatial distribution of the two most debilitating psychiatric illnesses within an epidemiologically complete population in County Monaghan is significantly non-random, reflecting the influences of specific social, economic or physical aetiological factors.

Methodology:

• To identify all existing cases of schizophrenia and bipolar disorder within the catchment area using current in-patient and outpatient records
• To attribute each patient to a DED within the study area by 'place of birth' and 'place of onset'.
• To calculate the annual prevalence rate for each DED, this is the maximum likelihood estimate of the underlying risk.
• To test whether the spatial distribution of these disorders within the study area is significantly non-random.
  Overall distribution of cases (total, male, female) will be tested for departures from a random distribution using Chi-squared statistics.
  Significance of the test statistic will be evaluated using Monte Carlo simulation test [10,000 repetitions].
  Evidence of significantly high or low prevalence rates in specific DEDs will be estimated by calculating a Poisson probability model.
  These estimates may be regarded as unstable if there is a small number of cases in some DEDs, thus empirical Bayes estimate (EBEs) will be calculated to alleviate this problem.
• Conduct a comparative analysis of the spatial distribution of schizophrenia and bipolar disorder by 'place at birth' and 'place at onset'.
• Analyse cases by gender to explore if different aetiological factors are at work using social indices from the Census of Population.
• To investigate the geochemistry i.e. the local bedrock, soil and hydrological profile, of the study area as a biogeochemical association between these disorders and the trace element selenium has been identified.

This research is funded by the Irish Research Council for the Humanities and Social Sciences, and NIRSA.