Even after two decades of decline, cigarette smoking remains the leading preventable cause of premature death and disease in the United States. And although fewer people are smoking cigarettes, more people than ever are smoking marijuana.
Previously Goodwin et al, (2017) revealed that marijuana use by cigarette smokers had increased dramatically over the past two decades, to the point where smokers are more than 5 times as likely as nonsmokers to use marijuana daily. These data support the controversial “gateway drug” hypothesis, assuming that cannabis is relatively benign compared to so called “harder drugs”, but using smoking marijuana often leads to the use of other drugs to the point of addiction.
Now the reverse seems to be true. Smoking marijuana is associated with subsequent cigarette smoking. A subsequent study, also by Goodwin and colleagues, showed that daily marijuana use occurs almost exclusively among nondaily and daily cigarette smokers compared with former and never smokers (8.03%, 9.01%, 2.79%, and 1.05%, respectively). Daily marijuana use has increased over the past decade among both nondaily smokers (8.03%  vs 2.85% ; linear trend P < .001) and daily smokers (9.01% ; 4.92% ; linear trend P < .001). Daily cannabis use increased most rapidly among former cigarette smokers (2.79%  vs 0.98% ; linear trend P < .001).
Why Does This Matter?
We have suggested for years that learning to inhale is, in fact, the critical gateway event. Why?
Because inhaling hot, noxious fumes defies every survival instinct inherent in every human and non-human mammal. To suppress one’s instinct to cough for the purpose of delivering a psychoactive substance to the brain is no small thing. Once a person can train themselves to override this most primitive and basic survival instinct, it sets them up for not only inhaling other drugs with relative ease, but also for addiction in general, because addiction requires the usurping of our survival drives in order to effect a mood change. The salience derived from using the drug becomes physiologically rewarding, to the detriment of the user.
As crazy as this sounds, smoking marijuana is now more socially acceptable than smoking cigarettes.
Andrea H. Weinberger, Jonathan Platt, Jan Copeland, Renee D. Goodwin. Is Cannabis Use Associated With Increased Risk of Cigarette Smoking Initiation, Persistence, and Relapse? The Journal of Clinical Psychiatry, 2018; DOI: 10.4088/JCP.17m11522