SCHIZOPHRENIA AMONG PATIENTS TREATED FOR RHEUMATOID-ARTHRITIS AND APPENDICITIS

The widely accepted negative association between schizophrenia and rhe umatoid arthritis (RA) is based on the results of investigations which sought RA in large samples of schizophrenic patients. Using a dischar ge register, we examined the frequency of schizophrenia in a sample of 5626 RA patients. Appendicitis patients (n = 5330) were used as a com parison group. The cumulative incidence of hospital care with the diag nosis of schizophrenia during 8 years was higher in the RA group (0.64 %) than in the appendicitis group (0.47%). Schizophrenia was significa ntly more common in the RA group than in the appendicitis group among the young. The age-adjusted prevalence of schizophrenia was 0.96% in t he RA group and 0.51% in the appendicitis group. Because of this unexp ected finding, we examined the incidence of RA and appendicitis among a birth cohort born in 1966, The frequencies of RA and appendicitis am ong schizophrenic cohort members (n = 76), cohort members with psychia tric diagnosis other than schizophrenia (n = 438), and members without psychiatric diagnosis (n = 10503) were similar. These findings do not support the negative association between schizophrenia and RA. Prolon ged institutionalization per se may have been the protective factor ag ainst RA in the previous studies. The findings also raise the hypothes is that genes that predispose to schizophrenia provide protection from appendicitis, historically a common cause of mortality. (C) 1998 Else vier Science B.V.