Further development of this finding has been taken on by the WHO International Study of Schizophrenia (ISoS). This is a collaborative project based on numerous cohorts including the original IPSS and Ten Country Study cohorts. Using the ISoS sample, Hopper and Wanderling (2000) replicated the developed versus developing differential both in the long term (>13 years follow-up), and under ICD-10 diagnostic criteria for schizophrenia. They demonstrated that various biases (ascertainment bias,  bias in loss to follow-up,  diagnostic issues including NARP and classification systems for developing/developed countries) could not account for the differences in outcome.

Possible explanations for differences in outcome

It appears, therefore, that some aspect of the economic or cultural circumstance in developing countries may provide a more therapeutic context for recovery.  The most commonly proposed explanations fall into four categories: family relationships, informal economies, segregation of the mentally ill and community cohesion. Family relationships Family relationships may be more conducive to recovery in developing country settings. In India and some other developing countries, families are closely involved in treatment, support, recuperation and rehabilitation of individuals with schizophrenia (Susser et al., 1996). An individual is never removed from the family’s care; social integration within the family setting is not disrupted.  Furthermore,  data support the view that family expressed emotion, a characteristic predicting relapse in developed country populations, may differ in developing country settings (Leff et al., 1987; Wig et al., 1987).

Informal economies
Students of developing countries often argue that, in subsistence economies, reintegration into work roles is the rule rather than the exception (Warner, 1985). Based on data from developed countries, reintegration into work roles would seem to be beneficial (Bell and Lysaker, 1997). In low-income countries, informal economies may provide more diverse opportunities for this reintegration to occur.

Segregation of the mentally ill
In developing countries, individuals with mental illness are less likely to be segregated in hospitals or other institutions. It has also been suggested that mental illness may be less stigmatized in developing countries, although there are no convincing data on this point.

Community cohesion
Communities may differ on dimensions of social integration and isolation, potentially creating contexts that are more or less therapeutic,  affecting chances for recovery.

Societal basis
The bases for each of these speculations are societal phenomena. That developing countries better serve those with schizophrenia than developed countries stands in contrast with what is known about the benefit to individuals of modern therapies (e.g. medication, family interventions), treatments often unavailable in these settings. One possible explanation is that societal level processes and system features of treatment as determinants of disease outcomes are responsible.

Conclusion
The contrasting experiences of developed and developing countries with respect to schizophrenia may be interpreted as providing evidence for socioenvironmental influences in this disorder. The findings in incidence rates are inconclusive; the evidence for differences in outcome, however, is clear and convincing.

Two main findings regarding the incidence of schizophrenia emerged from the landmark Ten Country Study:  first,  the incidence of schizophrenia narrowly defined showed little variation across sites; and second, the incidence of schizophrenia broadly defined was significantly higher in developing than developed country sites. The underpinnings of the narrow definition have been questioned, but the alternative posed by the broad definition is probably overinclusive. While we await incidence rates based on rediagnosis using modern diagnostic systems, the question of variation in incidence rates remains unresolved.

Course and outcome appear to be more favourable in developing countries. In light of the scarcity of treatment options, this finding is remarkable. A point deserving further investigation is that there may be a greater risk of adverse outcomes, as suggested by mortality rates in two developing countries.

Michaeline Bresnahan, Paulo Menezes, Vijoy Varma and Ezra Susser
Division of Epidemiology, Columbia University, New York, USA
Department of Preventative Medicine, University of Sao Paulo, Brazil

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