G. Morrison

Do symptom dimensions or categorical diagnoses best discriminate between known risk factors for psychosis

ObjectiveTo describe symptom dimensions of psychosis using detailed psychopathological information from epidemiologically defined incident cases which include the full spectrum of functional psychosis across all age ranges. Then, assess the comparative usefulness of the dimensional and categorical representations of psychosis in discriminating between demographic and pre-morbid risk factors.MethodA total of 464 incident cases of psychosis assessed with OPCRIT (Operational Checklist for Psychotic Symptoms) were included in an exploratory factor analysis. Using Regression analyses we modelled the associations of the dimensional and categorical representations of psychosis with antecedent validating variables and compared the subsequent models using the likelihood ratio test.ResultsFactor analysis produced five-symptom dimensions, manic, disorganisation, depressive, delusional and auditory hallucinatory symptoms, explaining 58% of the total variance. Different dimensions were differentially associated with the pre-morbid risk factors. Neither the dimensional nor the categorical representations on their own were sufficient to explain associations with the antecedent validating variables.ConclusionNeither the dimensional or the diagnostic representation of psychosis was superior in discriminating between known risk factors, combining dimensional measures with categorical diagnoses will probably be more informative in determining the causes and correlates of psychosis.

Nithsdale Schizophrenia Surveys 21: a longitudinal study of National Adult Reading Test stability

Background. The stability of the National Adult Reading Test (NART) as a measure of pre-morbid intelligence in schizophrenia has not yet been satisfactorily established despite the widespread use of the NART in schizophrenia research. Method. We examined NART stability in a diverse group of 45 schizophrenic patients in a prospective longitudinal study over 6·5–7·5 years. Results. The results showed that NART performance does not decline significantly with increasing duration of schizophrenic illness and that test–retest reliability, even over 6·5–7·5 years, is extremely high. Discussion. Our results provide the necessary evidence that the NART can be used as a stable measure of pre-morbid intelligence in schizophrenia.

Evidence that better outcome of psychosis in women is reversed with increasing age of onset: A population-based-5-year follow-up study

BACKGROUND Female gender and later onset of psychosis are both associated with better outcome. However whether their effects are independent, is not known. METHOD In 379 incident cases of psychoses, from an epidemiologically defined catchment area, admixture analysis was employed to generate age of onset classes. Five year course and outcome measured across clinical and social domains were used as dependent variables in regression analyses, to estimate associations of outcomes with gender, age of onset and gender by age of onset interaction. RESULTS Three age of onset classes were identified: early (14-41 years), late (42-64 years) and very late onset psychosis (65-94 years). Overall, women had better outcomes, including milder delusions, fewer negative symptoms, less deterioration from baseline functioning, fewer hospital readmissions and shorter psychotic episodes. Later age of onset was also associated with better outcome, although in the very late onset class the results were mixed. There was a statistically significant gender by age of onset interaction (in the ratio scale) within this sample with men displaying poorer outcome in the early/late onset class, whereas women tended to have a worse outcome in the very late onset class. CONCLUSIONS The favourable outcome in women becomes reversed in old age, suggesting gender-age-related differences in the distribution of aetiological factors for psychosis.

Nithsdale schizophrenia surveys 21: A longitudinal study of national adult reading test stability

BACKGROUND The stability of the National Adult Reading Test (NART) as a measure of pre-morbid intelligence in schizophrenia has not yet been satisfactorily established despite the widespread use of the NART in schizophrenia research. METHOD We examined NART stability in a diverse group of 45 schizophrenic patients in a prospective longitudinal study over 6.5-7.5 years. RESULTS The results showed that NART performance does not decline significantly with increasing duration of schizophrenic illness and that test-retest reliability, even over 6.5-7.5 years, is extremely high. DISCUSSION Our results provide the necessary evidence that the NART can be used as a stable measure of pre-morbid intelligence in schizophrenia.

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. AIMS 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. METHOD 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.