Behavioral determinants of condom use and HIV/STI testing in Chile: a theory-driven mixed-methods study.

Condom use and HIV/STI testing are essential prevention behaviors, yet uptake remains low in Chile. Using data from the 2022–2023 National Health, Sexuality, and Gender Survey (ENSSEX), this study applied a theory-driven mixed-methods approach to identify behavioral determinants influencing these practices among Chilean adults. Considering sexually active respondents, only 23.4% reported consistent condom use and 16.8% reported HIV/STI testing in the past 12 months. Behavioral barriers to condom use were primarily related to perceived reduction in sexual pleasure, social norms within stable relationships, and limited behavioral regulation, while HIV/STI testing was more strongly facilitated by knowledge-related factors but constrained by low-risk perception and structural access barriers. Integrating quantitative classification with theory-informed interpretation using the COM-B model and the Theoretical Domains Framework enabled the identification of key motivational, emotional, and contextual drivers underlying these behaviors. These findings highlight the need for prevention strategies that move beyond information provision to address emotional, social, and structural determinants of behavior. This approach provides actionable guidance for designing behaviorally informed HIV/STI prevention policies and interventions, and demonstrates the value of applying behavioral science frameworks to national survey data in Chile and other middle-income settings.