High Quality Content by WIKIPEDIA articles! An association between tobacco and other drug use has been well established. The nature of this association remains unclear. The two main theories are the phenotypic causation (gateway) model and the correlated liabilities model. The causation model argues that smoking is a primary influence on future drug use, while the correlated liabilities model argues that smoking and other drug use are predicated on genetic or environmental factors.A 1994 report from the Center on Addiction and Substance Abuse at Columbia University, found a correlation between the use of cigarettes and alcohol and the subsequent use of cannabis. The report asserted a link between alcohol and cannabis use and the subsequent use of illicit drugs like cocaine.