Abstract
Background: This study aimed to estimate the prevalence of substance use among university students measured by direct and indirect methods, and to calculate the visibility factor (VF) defined as ratio of indirect to direct estimates of substance use prevalence.
Study Design: A cross-sectional study.
Methods: Using a multistage non-random sampling approach, we recruited 2157 students from three universities in Kerman, Iran, in 2016. We collected data on substance use by individual face-to-face interview using direct (i.e. self-report of their own behaviors) and indirect (NSU: Network scale up) methods. All estimates from direct and indirect methods were weighted based on inverse probability weight of sampling university.
Results: The response rate was 83.6%. The last year prevalence of water pipe, alcohol, and cigarettes indirect method was 44.6%, 18.1%, and 13.2% respectively. Corresponding figures in NSU analysis were 36.4%, 18.2%, and 16.5% respectively. In the female population, VF for all types of substance was less than male.
Conclusions: Considerable numbers of university students used substances like a water pipe, alcohol, and cigarettes. NSU seems a promising method, especially among male students. Among female students, direct method provided more reliable results mainly due to transmission and prestige biases.
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