Revisiting the developed versus developing country distinction in course and outcome in schizophrenia: results from ISoS, the WHO collaborative followup project. International Study of Schizophrenia.

Abstract

This article examines the long-standing and provocative finding of a differential advantage in course and outcome for persons with schizophrenia living in "developing" countries, using results from the newly completed World Health Organization (WHO) collaborative project, the International Study of Schizophrenia (ISoS). The article addresses two questions: Has the differential survived the 13 years since it was last reported? If so, are the results demonstrably not attributable to artifactual confounding? The analysis focuses on the 809 subjects who make up the combined incidence cohort of ISoS. These include members of the original treated incidence cohorts of two earlier WHO studies (the Determinants of Outcome of Severe Mental Disorders and the Reduction of Disability Studies) as well as subjects drawn from two additional samples (Hong Kong and Madras/Chennai). We first review the consistency of the finding of a "developed versus developing" differential in course and outcome and then examine a variety of course and outcome measures for the ISoS incidence cohorts. Evidence of differences in illness trajectory in favor of the developing centers was consistently found. Six potential sources of bias are then examined: differences in followup, arbitrary grouping of centers, diagnostic ambiguities, selective outcome measures, gender, and age. None of these potential confounds explains away the differential in course and outcome. We conclude with suggestions for further research, with particular attention to the need for close documentation of everyday practices in the local moral worlds that "culture" refers to.