Abstract
Background: In developing countries, including Kazakhstan, formal sex education remains limited due to sociocultural norms, insufficient resources, and the absence of standardized curricula. Objective: This systematic review evaluates the effectiveness of school-based comprehensive sex education (CSE) interventions on adolescents' knowledge, attitudes, and sexual behaviors, and assesses their applicability within the Kazakhstani context. Methods: A systematic literature search was conducted in PubMed, PMC, Cochrane, Scopus, Web of Science, and Google Scholar for studies published up to October 2025. Eligible studies included interventions delivering CSE to children or adolescents and reporting outcomes related to knowledge, attitudes, or sexual behaviors. Primary outcomes included sexual and reproductive health knowledge, sexual behaviors, and biological outcomes (STIs, adolescent pregnancies), secondary outcomes included attitudes toward consent, gender equity, and psychosocial measures. Results: The search did not yield any studies from Kazakhstan or neighboring countries pertaining CSE. However, twelve studies met the inclusion criteria, including eight cluster-randomized controlled trials, two quasi-experimental studies, one cross-sectional study and a longitudinal observational study conducted across multiple countries. Overall, the included studies consistently reported improvements in sexual health knowledge and more favorable attitudes toward safe sexual practices following CSE interventions. A number of studies also indicated positive behavioral trends, such as delayed sexual initiation, increased contraceptive use, and reductions in risky sexual behaviors (e.g., multiple partners and unprotected intercourse), although the magnitude of these effects varied across studies. Conclusions: School-based CSE interventions appear to improve adolescents' knowledge, attitudes, and sexual behaviors in diverse contexts. Factors such as sociocultural might hinder the implementation of CSE in Kazakhstan. However, findings are based on heterogeneous study designs and should be interpreted with caution. At the same time, a culturally sensitive and context specific pilot CSE programs integrated into Kazakhstan's school curriculum, alongside teacher training and supportive health services is warranted.