investigating the prevalence of substance use among students of medical science universities in the eighth macro-region of iran

background: the growing trend of substance use among students is a serious threat for the health of young adults. using network scale-up (nsu) method objectives: the present study was designed to indirectly estimate the prevalence of substance use among students of medical science universities in the eighth macro-region of iran to attract government attention to this problem. materials and methods: this cross-sectional study was performed on 3,900 students from medical science universities in the eighth macro-region of iran (2300 from kerman and 1600 from sistan and baluchestan provinces) in 2019. the sample size of each university was determined using a multistage non-random sampling approach. the participants were asked to introduce their academic close friends who did high-risk behaviors during last year by researcher-made questionnaire. the chi-squared test was used for comparing two proportions. statistical analysis was carried out by excel and spss software version 19. significant level was set as 0.05. results: out of 3,900 participants, 1,872 (48%) were males and 2,028 (52%) were females. students from all academic degrees contributed to this study. the prevalence of alcohol, marijuana, hemp, chewing tobacco, tramadol, methylphenidate, and opium use were 20.6% (95% ci: 19.3 - 21.9), 13.5% (ci: 12.4 - 14.5), 4.1% (ci: 3.5 - 4.7), 6.3% (ci: 5.5 - 7.1), 3.1% (ci: 2.6 - 3.7), 6.5% (ci: 5.7 - 7.3), and 4.0% (ci: 3.1 - 4.9), respectively. also, the prevalence of substance use was higher among male students than females. conclusions: male students aremoreat risk for substance use. the rates of alcoholandmarijuana consumption were higheramong students. training programs are recommended to increase awareness level of young people and the society about disadvantages of these behaviors.