THE TOBACCO GATEWAY. “Nicotine use is a gateway to the use of marijuana and cocaine … In 2012, among U.S. adults 18 to 34 years of age who had ever used cocaine, 87.9% had smoked cigarettes before using cocaine, 5.7% began using cigarettes and cocaine at the same time, 3.5% used cocaine first, and 2.9% had never smoked cigarettes.”
http://www.nejm.org/doi/full/10.1056/NEJMsa1405092