It has been showed that higher exposure to secondhand smoking increased the risk of smoking. The multivariable logistic regression analysis showed that variables such as secondhand smoke at home, secondhand smoke at faculty, and secondhand smoke at public spaces can determine whether students smoke or not. It is also obvious that non-smokers avoid being in closed smoking places, but this was not subject of this study.
Second it a lack of analysis of second-hand smoke exposure. Specifically, whether exposure increases risk of smoking. Correlations do not confirm causality. It is likely that students who smoke actively seek roommates who smoke, and students who do not smoke seek roommates who do not smoke. Thus, exposure alone offers little information about the role of second-hand smoke and "contagion."