**Background:** The use of e-cigarettes among university students has increased globally, raising concerns about nicotine exposure and potential progression to illicit substance use, including cannabis. In Latin America, limited data exist on the association between e-cigarette and/or tobacco use and cannabis consumption among young adults. This study aimed to identify the association between lifetime tobacco and/or e-cigarette use and cannabis use in the last 12 months among Peruvian university students.
**Methods:** This was a secondary analytical cross-sectional study based on the III Andean epidemiological study on drug consumption among university students in Peru (2016). A random two-stage sampling was conducted: 10 universities agreed to participate (total population 145,081), and 21,144 students were randomly selected, with 4,259 responding and 3,981 meeting inclusion criteria (complete data on cannabis, e-cigarette, and tobacco use; age ≥18 years). The independent variable was lifetime e-cigarette and/or tobacco use, categorized as: only e-cigarettes, only tobacco, both, or neither. The dependent variable was self-reported cannabis use in the last 12 months. Covariates included age, sex, socioeconomic status, parental control, alcohol consumption, and illicit drug use. Multivariate analysis used a generalized linear model with log Poisson link, reporting prevalence ratios (PR) with 95% confidence intervals (CI). The study had >80% power.
**Key Results:** Among 3,981 participants (51.2% male; mean age not clearly reported), lifetime prevalence of tobacco use was 53.1% (95% CI: 50.5–55.7), e-cigarette use was 12.7% (95% CI: 11.2–14.5), and cannabis use in the last 12 months was 5.2% (95% CI: 4.1–6.5). Lifetime dual use of e-cigarettes and tobacco was 11.6% (95% CI: 10.1–13.3), only tobacco was 41.5% (95% CI: 38.9–44.2), only e-cigarettes was 1.2% (95% CI: 0.7–1.8), and neither was 45.7% (95% CI: 43.1–48.4). In the adjusted analysis, dual users had 58.5 times higher probability of cannabis use (PRa 58.5, 95% CI: 20.9–163.7, p <0.001), exclusive tobacco users had 33.3 times higher probability (PRa 33.3, 95% CI: 11.9–93.2, p <0.001), and exclusive e-cigarette users had 9.8 times higher probability (PRa 9.8, 95% CI: 1.6–60.4, p = 0.014) compared to non-users. Other significant factors included illicit drug use (PRa 3.1, 95% CI: 2.0–4.9, p <0.001) and younger age (21–22 years: PRa 3.5, 95% CI: 1.7–7.2, p = 0.001; 19–20 years: PRa 3.3, 95% CI: 1.6–6.8, p = 0.002; 18 years: PRa 3.1, 95% CI: 1.5–6.4, p = 0.002).
**Clinical Implications:** This study demonstrates a strong, graded association between lifetime nicotine product use (e-cigarettes and/or tobacco) and recent cannabis use among Peruvian university students. The sequential probability gradient—highest for dual users, followed by exclusive tobacco users, then exclusive e-cigarette users—suggests that nicotine exposure may facilitate progression to cannabis use, possibly through neurological, behavioral, and social mechanisms. These findings underscore the need for public health interventions targeting nicotine product use among young adults, including stricter regulation of e-cigarettes, educational campaigns about the risks of progression to illicit substances, and further research in diverse cultural contexts to explore causality, dosage, and concurrent use patterns.