This study confirms high rates of substance misuse at onset of psychosis. There is evidence for an increase in diagnosis of substance-related psychotic disorders over time. Those most at risk of substance misuse are young males.

The size of the increase and the methodological safeguards employed support the validity of this now highly replicated finding. A personal or family history of migration from the Caribbean is a major risk factor for psychosis; the consistency of this finding justifies a systematic evaluation of potential aetiological factors. Any hypothesis derived from the evidence so far must explain: increased incidence in first and second generation migrants; increased risk for all psychoses (including affective psychoses); and an effect specifically associated with a migration history from the Caribbean to Northern Europe.

The findings reported are similar to those of other long-term follow-up studies of schizophrenia and also to 5-year follow-up studies. Kraepelin's emphasis on the longitudinal implications of a diagnosis of schizophrenia are supported, but may be over-pessimistic.

Methodological considerations call for caution in interpreting such data, but we conclude that the significant fall in the narrowly defined diagnostic category of schizophrenia reflects a real change in the syndromal presentation of psychotic disorders.

The data presented are those from a two-year prospective study of 69 patients identified in the Nottingham field centre of the WHO Study of Determinants of Outcome of Severe Mental Disorders. Premorbid personality, childhood adjustment and adolescent adjustment were assessed at the patients' first presentation to psychiatric services with a psychotic illness. Ratings were made blind to diagnosis. Premorbid explosive and paranoid traits were commoner in patients with schizophrenia than in patients with other non-organic psychoses, and these traits were associated with later onset of schizophrenia. Premorbid schizoid traits were significantly commoner in patients with schizophrenia compared to patients with other psychoses, but only in those patients for whom a parent was the informant. Schizoid traits were no commoner in men with schizophrenia than in women, and were not associated with earlier age of onset. The findings suggest that premorbid personality, in men and women, may shape the expression of symptoms produced during an illness episode.