Objectives: To evaluate the situation of depression in developing countries, establishing the main factors associate to this highly prevalent disorder. This review focus in population-based studies, since they are the more reliable sources of prevalence/ incidence estimates and its correlated factors.

Methods: A systematic review was undertaken, with a comprehensive search of the literature, including Medline and Lilacs databases, and cross-checking the references from identified studies. Population-based studies that evaluated depressive disorders and/or minor psychiatric disorders were included and its results are presented and discussed according to a hierarchical model of disease causality in deprived countries.

Results: 26 studies (45,967 subjects) were included (25 cross-section, and 1 case-control). Depression rates ranged from 3% (in a Brazilian city) to 44.4% (in a Pakistanis village). These differences can be partially explained by social conditions and the instruments used to measure psychiatric disorders. The main associated factors to depression are female gender, higher age, poor education, low income, poor social support and stressful life events.

Conclusion: To establish a target population more susceptible to develop depression is a major task for those who have to plan the distribution of resources for preventing and treating such a highly prevalent and severe disease. Improving general social and health conditions and providing social equalities would be the main challenge to modify the situation of depression in deprived countries.