Drug use during college can have substantial harm on students’ lives and impacts the institutions’ functioning and local communities. Yet existing interventions for drug use at college poorly address the concurrent dynamic influences of the experiences in earlier developmental periods of young adults and the proximal contextual triggers of college life; both risk factors that contribute to drug use. In answer to this, system dynamic methods and contextual-behavioural science (CBS) approaches can support the development of interventions to address these risk factors. Using Causal Loop Diagram methods (Vensim PLE), we collected qualitative data from college students (n=24, aged 22 years old), during the development phase of MyUse: a contextual behavioural change intervention for harm reduction practices at college students, to generate Network Feedback Loops (NFLs). The findings underscore central nodes (determinants within an intervention) that can support our previous identified three CBS-harm-reduction practices for college students (targeted edges: mindful drug-use decision making, value-based activities, context-sensitive personalized plan of harm reduction). Analyses revealed 4 NFLs for students with previous drug use, consisting of 13 edges (4 positive, 2 negative, and 4 balancing reinforcing relationships) and 3 NFLs for students with no previous drug use, consisting of 4 positives, one negative, and one balancing relationship. All these determinants (manipulable variables) are nested with the three CBS-related targeted outcomes. College students who use drugs need drug-related knowledge about the unpredictable and adverse effects of drugs, presented in a compassionate way and distributed from credible resources (e.g., students’ unions/ club). Students with no previous drug use need education about the effects of drugs and awareness of how drugs can devaluate value-based activities (e.g. sports, friendships, social life). These should be delivered via proxy cue reminders and mobile-text-messages conveying drug use susceptibility, distributed in real-time. Idiosyncratic, dynamic, and contextual-bound factors of lapse risks or preventive practices should account for each person-specific vulnerabilities via personalized harm reduction plans.