Abstract Background Cognitive dissonance theory and research has suggested that engaging in prevention interventions for other students may be a means of reducing one’s own problematic behaviors in order to reduce potential cognitive dissonance. This study assessed the effects of a new mandatory prevention intervention program for healthcare students in France. The aim was to measure the effects of engaging in a prevention program in schools on the usual increase in substance use in student populations. Methods Healthcare students were trained in a French university to develop psychosocial competences as a health promotion means (FEPS training) or more specifically to prevent substance use in teenagers (Unplugged program training). The students ( n = 314) who accepted to take part in the study from both groups completed questionnaires before their interventions in schools, and at the end of the year, measuring their representations and behaviors regarding psychoactive substances. Results The results indicated a significant reduction in alcohol consumption in terms of quantity, but no significant reduction in tobacco and marijuana consumption. Conclusions This study showed that, contrary to the usual increase in substance use in students as they advance in their year, the students who took part in this study showed reduced self-reported consumption of alcohol after they had performed the prevention intervention in schools regardless of the type of training they had received (general health promotion vs. specific substance use prevention program). Limitations and future perspectives are discussed.