The Northern Ireland First-Episode Psychosis Study has shown that the incidence of psychosis and schizophrenia is slightly higher than that found in recent studies in Ireland and Nottingham.
As anticipated, men had a higher rate of schizophrenia than females. But in contrast to most previous studies, there was no evidence of an increase in psychosis or schizophrenia in urban areas. The researchers believe that this finding is likely to reflect particular socio-economic factors in Northern Ireland.
Despite substantial population research into psychosis, there remains a debate on key questions, in particular the influence of gender and urbanisation on incidence.
This study carried out a prospective assessment of cases of psychosis presenting for the first time to adult psychiatric services within a two-year period.
Subjects were aged 18-64, with no obvious organic cause for their psychotic symptoms. The diagnosis was confirmed at one-year follow-up.
327 cases were identified, of whom 77% agreed to participate in the study. The incidence of psychosis in the study area was found to be 3.3 at risk per year per 10,000 population.
Men had a 1.8 times increased incidence of psychosis relative to females, and 2.7 times increased incidence of schizophrenia. The average age of diagnosis was around 29 for both men and women.
The incidence of psychosis and schizophrenia in the Belfast urban area was similar to that in rural areas. There was a significant rate of substance misuse (40%) among those studied, the most common substances used being alcohol and cannabis. However, only 9% of all cases seemed to have a specific drug-induced psychosis.