RESUMO
OBJECTIVES: To demonstrate a study design that could be useful in low-resource and violent urban settings and to estimate the prevalence of child violence exposure (at home, community, and school) and child mental health problems in a low-income medium-size city. METHODS: The Itaboraí Youth Study is a Norway-Brazil collaborative longitudinal study conducted in Itaboraí city (n = 1409, 6-15 year olds). A 3-stage probabilistic sampling plan (random selection of census units, eligible households, and target child) generated sampling weights that were used to obtain estimates of population prevalence rates. RESULTS: Study strengths include previous pilot study and focus groups (testing procedures and comprehension of questionnaire items), longitudinal design (2 assessment periods with a mean interval of 12.9 months), high response rate (>80%), use of standardized instruments, different informants (mother and adolescent), face-to-face interviews to avoid errors due to the high frequency of low-educated respondents, and information gathered on a variety of potential predictors and protective factors. Children and adolescents presented relevant levels of violence exposure and clinical mental health problems. CONCLUSIONS: Prevalence estimates are probably valid to other Brazilian low-income medium-size cities due to similarities in terms of precarious living conditions. Described study methods could be useful in other poor and violent world regions.