First-episode psychosis: diagnostic stability over one and two years.

BACKGROUND

Diagnostic stability is important for daily clinical work and planning of treatment. The aims of this study were to measure diagnostic stability in a clinical epidemiologic sample and to identify markers of change in diagnosis.

SAMPLING AND METHODS

Diagnostic stability and change were measured in a sample of 301 patients with first-episode psychosis from four national health care sectors in Norway and Denmark at baseline, 1 and 2 years.

RESULTS

Diagnostic stabilities were high for schizophrenia and schizoaffective disorder (85-99%), low for schizophreniform disorder (16-19%), and intermediate for other diagnoses. Diagnostic change from schizophreniform to schizophrenia was frequent in year 1 (72%). Characteristics discriminating schizophreniform patients keeping their diagnosis (i.e. having recovered within 6 months with no relapse) from those developing schizophrenia at 1 year were female gender, better childhood premorbid functioning, shorter duration of untreated psychosis and more severe general psychotic symptoms, especially excitation.

CONCLUSIONS

Findings provide validation for the DSM-IV categories within the schizophrenic spectrum. The limitations of the study were: the raters were not blind to baseline assessments; patients with longer duration of untreated psychosis were more likely to refuse participation; not all patients were assessed at 1- and 2-year follow-up, but the attrition was rather low.