**Background:** Sexuality is a central dimension of adolescent development with significant implications for physical and mental health. Negative sexual experiences during adolescence can lead to sexually transmitted infections (STIs), unintended pregnancy, intimate partner violence, depression, and anxiety. Sexuality education interventions (SEIs) are widely used to promote sexual health, yet there is substantial variability in their components, and the key elements that make them effective remain unclear. Three main approaches exist: abstinence-only/abstinence-plus, comprehensive (covering biological, psychosocial, and rights-based aspects), and risk-oriented (focusing on biological risks and prevention). Beyond approach, other components include theoretical framework, intervention type (individual vs. group; single-sex vs. mixed-sex), dose (number and length of sessions), methodology (expository vs. participatory), and facilitator training. This systematic review aimed to identify shared components of successful A-SEIs through RCTs published in the last ten years.
**Methods:** The review followed PRISMA guidelines. A search was conducted in CINAHL, PsycInfo, PubMed, and Web of Science between November and December 2021. Inclusion criteria were: studies published from 2011 onwards; written in English or Spanish; universal preventive in-person SEIs targeting adolescents aged 11–19; RCT design; and at least one statistically significant positive outcome. Exclusion criteria included non-empirical designs, remote/computer-based interventions, and interventions including parents or high-risk populations. Two researchers independently screened titles, abstracts, and full texts. Of 9131 initial records, 813 duplicates were removed, leaving 8318 reports. After title screening (7306 excluded), abstract review (649 excluded), and full-text screening (336 excluded), 27 studies remained. These were evaluated with the Jadad scale; 21 studies scoring ≥3 points were included. Data were coded for intervention characteristics including approach, dose, theoretical framework, type, methodology, facilitator training, and outcomes.
**Key Results:** A total of 18 interventions were identified across the 21 included studies. Most interventions (72.22%, n=13) used a comprehensive approach; 22.2% (n=4) used a risk reduction approach; and 6% (n=1) used an abstinence-plus approach. Regarding dose, the number of sessions ranged from 1 to 25: 44.44% had 11–16 sessions, 22.2% had 5–9 sessions, 17% had 21–25 sessions, and 17% had 1 session. Total intervention hours ranged from 1 to 26: 50% had 10–19 hours, 22.2% had 1–5 hours, and 11.1% had 25–36 hours. Of interventions with more than one session, 60% were delivered weekly. For theoretical frameworks, 61.1% of interventions used Ajzen's theory of planned behavior or the theory of reasoned action; 39% used Bandura's social cognitive theory; and 39% incorporated two or more theories. All interventions were delivered in groups; 94.4% targeted mixed-sex groups, and only one intervention (5.6%) was single-sex (African American female adolescents). Participatory-interactive methodology was used in 94.4% of interventions, including icebreakers, games, role-plays, group discussions, and critical thinking activities. Facilitator training was provided in 94.4% of interventions, ranging from two days to two weeks, covering curricula, protocols, and sensitive question handling. Outcomes spanned three domains: psychosocial outcomes (improved attitudes toward condom use, partner communication, self-efficacy, reduced intimate partner violence), knowledge (increased knowledge of sexual/reproductive health, STI transmission, contraception), and preventive sexual behaviors (delayed sexual initiation, reduced unprotected sex, fewer partners, increased condom and contraceptive use).
**Clinical Implications:** This review provides evidence-based guidance for designing effective adolescent sexuality education interventions. The five shared components of successful A-SEIs are: (1) grounding in behavior change theoretical models (theory of planned behavior, theory of reasoned action, or social cognitive theory); (2) use of participatory, interactive methodology; (3) delivery to mixed-sex groups; (4) comprehensive facilitator training with modeling and feedback; and (5) at least 10 hours of weekly intervention. The predominance of the comprehensive approach (72%) supports its effectiveness over abstinence-only or risk-oriented approaches. Notably, none of the interventions that addressed gender reported specific gender-related outcomes, highlighting a gap in measurement. The review was limited by the absence of studies from Latin America and Asia meeting quality criteria, though some studies included Hispanic/Latino and Asian participants. These findings can inform the design and adaptation of future A-SEIs, though further research including meta-analyses is needed to detect moderating factors.