[Internal migration and mental disorders: new evidence for an old hypothesis]

The relationships between migration and mental illness have been perhaps the most important research topic of Social Psychiatry. Studies on this issue conducted in Latin America have in general reached the conclusion that migration, and the experience of modernization related to it, is a major risk factor of emotional disturbance. This hypothesis was tested with data from a survey based on a representative sample of 1549 adults living in a low-income neighborhood in Bahia, Brazil. The survey employed the QMPA, a 43-item symptom scale which was developed and tested especially for studies in that sociocultural setting; it showed high sensitivity (.93) and specificity (.72) and adequate overall misclassification rate (.12). Seven trained interviewers applied a family questionnaire (20 items on demographic and socioeconomic information) and the QMPA to all the families (493) in the sample. Multiple classification analysis and covariance analysis were used to control for the effect of potential confounding factors. Crude analyses showed a statistically significant association between migration status and poor mental health. However, taking into account the combined effect of age, marital status and education as confounders resulted in non-significant levels for the association under study. Sex and economic position, despite being themselves related to emotional disturbances, did not appear as confounders or interaction terms in these analyses. The results on rural-urban origin did not provide any evidence in support to the modernization hypothesis.