Depression among Brazilian adolescents: a cross-sectional population-based study

Depression is the most common mental disorder during adolescence. Mental disorders often begin between infancy and adolescence, persisting throughout the rest of life and even affecting the well-being of subsequent generations.

This was a cross-sectional population-based study, with two-stage, probability-proportional-to-size cluster sampling, conducted in the city of Pelotas, in southern Brazil. All individuals aged 10-19 years and living in the selected dwellings were invited to participate in the study. To identify depression, we applied the Patient Health Questionnaire-9. We defined minor depression as the presence of two or more depressive symptoms, at least one of which is depressed mood or anhedonia. The symptoms were considered valid only if reported to persist for a week or more or to occur nearly every day, the exception being suicidal thoughts, which was considered valid regardless of frequency.

We interviewed 743 adolescents, among whom the prevalence of minor depression was 17.0% (95% confidence interval, 14.0-20.0), being higher among girls than among boys, as well as among individuals aged 14-15 years, those self-identifying as an ethnic minority, those who were smokers and those who lived with a depressed individual.

The reverse causality bias that is a problem inherent to cross-sectional studies, which precluded the establishment of temporal relationships between exposures and the outcome of interest.

Our results illustrate the relevance of depression in adolescents, underscoring the need for mental health policies targeting this population, with the objective of minimising the short- and long-term effects of early-onset depression.