Objective: Cigarette smoking has declined in the United States. Still, identifying prevalent and modifiable barriers to quitting can help inform the next steps for tobacco control. Illicit drug use, which may be increasingly common in the United States, could be one such factor. We investigated the relationship between past-month illicit drug use and cigarette smoking status and estimated trends in the prevalence of past-month illicit drug use by cigarette smoking status from 2002 to 2014 in the United States.

Methods: The 2002-2014 National Survey on Drug Use and Health was used to obtain nationally representative data on past-month illicit drug use.

Results: From 2002 to 2014, past-month illicit drug use (for all drugs considered) was nearly 5 times more common among current smokers than among never smokers (adjusted odds ratio = 4.79) and nearly twice as prevalent in former smokers as in never smokers (adjusted odds ratio = 1.99). Illicit drug use increased linearly over time from 2002 to 2014 in the entire general population (ie, across and within current smokers, former smokers, and never smokers). This increasing trend in drug use was most rapid among former smokers (relative to current smokers and never smokers) and was largely, but not entirely, driven by increases in cannabis use.

Conclusions: Illicit drug use is most prevalent among current cigarette smokers. Yet, the rate of increase in illicit drug use prevalence was most rapid among former smokers. Because former smokers outnumber current smokers in the general population, it may be important to monitor former smokers into the future for potential negative drug-related outcomes.