Because youth less than 16 years old are less likely to use or have access to contraception, they are at a high risk for STDs and unintended pregnancy (Mathews et al., 2009).Global research on sexual and reproductive health indicates that the prevalence of sexual activity varies markedly between boys and girls and across countries (Avery & Lazdane, 2010; Centers for Disease Control and Prevention, 2014). In 2015, a national survey in Brazil found that 34.5% of boys and 19.3% of girls between ages 13 and 15 had engaged in sexual intercourse. Younger adolescents are also at higher risk for unsafe sex at first sexual intercourse compared to older adolescents; In Brazil, condom use was less prevalent among adolescents aged 13 and 15 (59.7%) when compared to 16 and 17 year old adolescents (68.2%) (National Survey of School Health; PENSE) (IBGE, 2016). Unsafe sex is also more frequent among Brazilian adolescents from households with few socioeconomic assets (Oliveira-Campos, Giatti, Malta, & Barreto, 2013).Both substance use and parenting styles influence early sexual initiation. US studies show that alcohol, tobacco and marijuana use were associated with sexual activity at the age of 15 (Connell, Gilreath, & Hansen, 2009). At the same time, research suggests adolescents with authoritative mothers are less likely to have had sexual intercourse when compared to adolescents with any other parenting style (Pittman & Chase-Lansdale, 2001). However, few studies have examined these risk behaviors in the Brazilian context

Sexual risk behaviors are closely related to the use of alcohol, tobacco, and other illicit drugs as well as teen dating violence. School-based drug prevention programs that teach social and personal skills could potentially also reduce sexual risk behaviors. We examined the effects of the #Tamojunto program on youth sexual risk behaviors. A randomized controlled trial was conducted with 6391 7th and 8th grade students in 72 public schools in six Brazilian cities. Baseline data were collected prior to program implementation. Two waves of follow-up assessments occurred after 9 and 21 months. Analyses were performed taking into account the multilevel structure of the data. We used intention-to-treat to evaluate changes in the prevalence of sexual risk behaviors over time and between groups. Adolescent age ranged from 11 to 15 years, with a mean of 12.6 ± 0.8 years, and 51.0% were female. Among all participants, receipt of #Tamojunto was associated with higher risk of lifetime sex at 21 months follow-up (OR 1.27, 95% CI [1.03, 1.56]). Among girls, at 9 months follow-up, the program was associated with higher likelihood of having engaged in sex in the last month (OR 1.76, 95% CI [1.13, 2.74]). At 21 months follow-up, girls receiving the program were more likely to report engaging in condomless sex in the last month (OR 1.64, 95% CI [1.07, 2.50]). #Tamojunto may be ineffective and possibly harmful for preventing sexual risk behaviors, especially among girls. We suggest further investigation of the possible mediating role of life skills intervention components on girl's sexual behaviors.

This systematic review provides a comprehensive assessment of risk factors related to early sexual intercourse (ESI) among adolescents. We used PRISMA guidelines to identify eligible cohort studies published between January 1999 and December 2020. We searched on three databases: PubMed, Embase and LILACS. Studies were screened for quality and eligibility. Of 2787 identified studies, seven met our inclusion criteria. The studies examined a range of factors, which were organized into four dimensions – individual, family, social and environmental, and sociodemographic. Risk factors with strong associations for ESI were: adolescent and parental substance use, aggression and conduct disorders, family attachment, school achievement, family living situation, and maternal education. Three studies were birth cohorts. This review demonstrates the important roles of substance use, family attachment and academic factors in shaping adolescents’ sexual behavior. A strength of this review is its focus on longitudinal studies, enabling exploration of exposures collected before initiation of sexual intercourse. Supplementary Information The online version contains supplementary material available at 10.1007/s10578-023-01519-8.

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