The title of a recent article stated that smoking is actually increasing over time in those using illegal drugs (Addiction 113:719). But when I read it, found that it was more complicated than that. Seems that cigarette use in those with opioid, cocaine, etc dependence increased over time from 61% in 2002 to 68% in 2014 (ie.by 0.6%/yr). But then smoking in those with cannabis dependence (which is 6 times more common) was decreasing over time at a rate even greater than that in the general public! Since marijuana decriminalization has been increasing since 1973 (and it’s decriminalization that effects marijuana use more than legalization) and since marijuana and tobacco are “complements” (when use of one increases the use of the other also increases), tobacco use should go up over time in marijuana users. So I Iooked into studies of the effect of marijuana legalization on smoking. No longitudinal studies have been done. One cross-sectional study (Drug Alcohol Depend 166:32) found that use of both marijuana and tobacco use was greater in states with medical marijuana. But then another paper found that between 2003 and 2012, marijuana use among tobacco users increased from 14% to 18% (a 0.4%/year increase) – which plausibly could be due to marijuana laws. But tobacco use among marijuana users decreased from 74% to 70% (a 0.4% decrease), – which plausibly could be due to efforts to decrease smoking.
It will be very important to track smoking after marijuana law changes, as even a 2% increase in tobacco use would have big public health implications. I hope some longitudinal studies come out soon.