Schizophrenia is not disappearing in south-west Scotland.
BACKGROUND
Recent work has reported a decline in the incidence of schizophrenia, but it is unclear if these findings reflect a true decrease in its incidence or are an artefact arising from methodological difficulties.


OBJECTIVE
To take account of these methodological difficulties and report service-based incidence rates for schizophrenia in Dumfries and Galloway in south-west Scotland for 1979-98.


METHODS
Using both clinical diagnoses and diagnoses generated from the Operational Checklist for Psychotic Disorders (OPCRIT) computer algorithm for ICD-10 and DSM-IV schizophrenia, we measured change in the incidence rates over time. We used indirect standardisation techniques and Poisson models to measure the rate ratio linear trend.


RESULTS
There was a monotonic and statistically significant decline in clinically diagnosed schizophrenia. The summary rate ratio linear trend was 0.77. However, using OPCRIT-generated ICD-10 and DSM-IV diagnoses, there was no significant difference over time.


CONCLUSIONS
OPCRIT-generated consistent diagnoses revealed no significant fall in the incidence of schizophrenia. Changes in diagnostic practice have caused the declining rates of clinically diagnosed schizophrenia in Dumfries and Galloway.
Allardyce
J
J
Department of Clinical Research, Crichton Royal Hospital, Dumfries, Scotland, UK. j.allardyce@clinmed.gla.ac.uk
Morrison
G
G
Van Os
J
J
Kelly
J
J
Murray
R M
RM
McCreadie
R G
RG
D005163:Factor Analysis, Statistical; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D012559:Schizophrenia / Q000175:diagnosis / Q000453:epidemiology*; D012606:Scotland / Q000453:epidemiology