Depressão e inteligência na adolescência

Abstract

The thesis aimed to study the intelligence quotient (IQ) and depression during adolescence. The thesis consists of two parts. The first part aimed to assess the effects of an early childhood nutrition counselling intervention on intelligence at age 15–16 years. This was a single-blind, cluster randomised trial. In 1998, in Southern Brazil, mothers of children under two received a nutrition counselling intervention (n=424). Counselling included encouragement and promotion of exclusive breastfeeding until 6 months of age and continued breastfeeding supplemented by protein-, lipid-, and carbohydrate-rich foods after age 6 months up to age 2. The control group received routine feeding advice. In 2013, the fourth round of follow-up of these individuals, at the time with a mean (SD) age of 15.4 (0.5) years, was undertaken (n=339). IQ was assessed using the short form of the Wechsler Adult Intelligence Scale (WAIS-III). Mean total IQ scores were 95.8 (11.2) in the control group and 93.4 (11.4) in the intervention group. Adjusted analysis revealed no difference between the intervention and control groups (p=0.362). In this sample, a nutrition counselling intervention in early childhood had no effect on intelligence measured during adolescence. The objective of the second part of the thesis was to assess the prevalence of minor depression, as well as the associated demographic, socioeconomic and behavioural factors, among Brazilian adolescents. This was a cross-sectional population-based study, with two-stage, probability-proportional-tosize cluster sampling, conducted in the city of Pelotas, in southern Brazil. 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. 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.