Comportamento sexual e uso de substâncias psicoativas em adolescentes brasileiros: fatores contextuais associados

Abstract

Introduction: Evidence shows that family and school are the contexts with which the adolescents interacts most and have more influence on their behaviours. Risky sexual behaviour and use of psychoactive substances are two major public health problems among adolescents worldwide and in Brazil. There is little evidence regarding the role of these contexts on risky behaviours among adolescents in Latin America. This is a pioneer study on the influence of family and school contexts on sexual behaviour and combined use (cluster) of psychoactive substances among adolescents in the country. Objectives: The objectives of this thesis are threefold. The first one is to describe the sexual behaviour of students of the 9th school grade and to identify family and school factors associated with having sex with or without use of condom. Second, to estimate the prevalence of early intercourse among 14-years-old students and to identify contextual factors in the family, school and surroundings associated with this behaviour. The third objective is to investigate the cluster of psychoactive substance use among children of the 9th year grade and the contextual factors associated with this cluster. Methodology: All 60,973 adolescents participants of the National Survey of School Health in 2009 (PeNSE 2009) were included. They are a representative sample of all students enrolled in the 9th grade of public and private schools, attending day shifts, and were selected by a two-stage sampling in 26 state capitals and the Federal District. Three articles were produced, each one dealing with one of the study objectives. In the first article, the response variable was the sexual behaviour described in three categories (never had intercourse, had intercourse with protection, had unprotected sex). Multinomial logistic regression was used to identify the contextual variables associated with protected and unprotected sex, having "never had sex" as the reference category. In the second article, this study was restricted to teenagers aged 14 years (n=27,243). The early intercourse (yes/no) was described and the variables associated with this behaviour were identified by means of multiple logistic regression analysis. They included socio-demographic characteristics, substance use, and involvement in fights, family factors and school and surroundings factors. The third article had a response variable defined by a combination of no substance use, use of tobacco and/or alcohol and/or illicit drug experimentation. The cluster of psychoactive substances was grouped into four categories: no use of psychoactive substance, one, two or three psychoactive substances. The explanatory variables were: demographic characteristics, behavioural risk factors, family background and school factors. The variables associated with the cluster of psychoactive substances in each context were investigated through multinomial logistic regression analysis, taking as reference the category "no psychoactive substance." Results: The first study shows that about a quarter of adolescents had sexual intercourse in lifetime, being more frequent among boys than girls. Among adolescents who reported sexual initiation, the majority held their first sexual intercourse up to 13 years of age. About 21 % did not use condom at the last sexual relation, and the chance of protected and unprotected sex increased with the number of healthy risk behaviours presented. In the family context, living with one or no parent and low parental monitoring increased the chances of both protected and unprotected sex, and never having meals with parent(s) of unprotected sex. Adolescents enrolled at private schools had less chance of protected and unprotected sex and not receiving information on pregnancy prevention at school increased the chance of having sex, with greater magnitude of the Odds Ratios for having unprotected sex. The second article shows that about one quarter of 14-year-old adolescents had already had sexual intercourse. The chance of early intercourse was lower among students from private school and who reported having received information about preventing pregnancy and / or STDs at school. In the family context, living with only one or no parent, having low parental monitoring and family assault was associated with increased odds of early intercourse. There is a dose-response gradient increasing associations between the number of absences from school without parental permission and the number of absences due to insecurity in school and / or on the way home from school and the chance of early intercourse. The third study found that 23 % of teenagers had used one psychoactive substance, 5.3% two, and 2.9% three substances. Students who had indicators of vulnerability in family relations, from public schools and who had other risk behaviours such as early sexual intercourse, unprotected sex, engagement in fights with weapons, had greater chances of using more psychoactive substances, with greater odds ratios for using three substances. Conclusions: The results show that a high percentage of teens are engaging in risky behaviour in the early stages of adolescence, with emphasis on the current use of alcohol. Most adolescents who use psychoactive substances are involved in other risky behaviours such as early sexual intercourse, unprotected sex and involvement in fights with weapons. Worse family background and school indicators negatively affect adolescents health behaviours, increasing the chance of risk sexual behaviour and involvement with substance use. Vulnerable family contexts and lack of information on sexual and reproductive health at school are associated with early sexual intercourse and unprotected. Furthermore, the presence of a risk factor tends to increase the chance of exposure to another risky behaviour, in an intricate and dynamic way, indicating the need to integrate the approach of these factors, and the involvement of families and schools is essential to obtain success.