Mixing tobacco and marijuana may seem like a good idea, but here's the dangerous truth about blunts

People who smoke a combination of tobacco and marijuana, a common practice overseas for years, and increasingly popular here in the form of "blunts," may be reacting to some unidentified mechanism that links the two drugs.
Researchers believe such smokers would be well advised to consider giving up both drugs at once, rather than one at a time, according to an upcoming study in the journal Addiction.

Clinical trials of adults with cannabis use disorders suggest that "approximately 50% are current tobacco smokers," according to the report, which was published in the journal Addiction, and authored by Arpana Agrawal and Michael T. Lynskey of Washington University School of Medicine, with Alan J. Budney of the University of Arkansas for Medical Sciences.

"As many cannabis users smoke a mixture of cannabis and tobacco or chase cannabis use with tobacco, and as conditioned cues associated with smoking both substances may trigger use of either substance," the researchers conclude, "a simultaneous cessation approach with cannabis and tobacco may be most beneficial."

A blunt is simply a marijuana cigar, with the wrapping paper made of tobacco and the majority of loose tobacco removed and replaced with marijuana. In Europe, smokers commonly mix the two substances together and roll the combination into a single joint, the precise ratio of cannabis and nicotine varying with the desires of the user.

“There is accumulating evidence that some mechanisms linking cannabis and tobacco use are distinct from those contributing to co-occurring use of drugs in general,” the investigators say. Or, as psychiatry postdoc Erica Peters of Yale put it in a press release, "There's something about tobacco use that seems to worsen marijuana use in some way."

The researchers believe that this "something" involved may be a genetic predisposition. In addition to an overall genetic proclivity for addiction, do dual smokers inherit a specific propensity for smoked substances? We don't know—but evidence is weak and contradictory so far.
 
Flickr/Torben Hansen
Wouldn't it be easier to quit just one drug, using the other as a crutch? The researchers don't think so, and here's why:
In the few studies available, for every dually addicted participant who reported greater aggression, anger, and irritability with simultaneous cessation, "comparable numbers of participants rated withdrawal associated with dual abstinence as less severe than withdrawal from either drug alone." So, for dual abusers, some of them may have better luck if they quit marijuana and cigarettes at the same time. The authors suggest that "absence of smoking cues when abstaining from both substances may reduce withdrawal severity in some individuals."

In other words, revisiting the route of administration, a.k.a. smoking, may trigger cravings for the drug you’re trying to quit. This form of "respiratory adaption" may work in other ways. For instance, the authors note that, "in addition to flavorants, cigarettes typically contain compounds (e.g. salicylates) that have anti-inflammatory and anesthetic effects which may facilitate cannabis inhalation."

Studies of teens diagnosed with cannabis use disorder have shown that continued tobacco used is associated with a poor cannabis abstention rate. But there are fewer studies suggesting the reverse—that cigarette smokers fair poorly in quitting if they persist in cannabis use. No one really knows, and dual users will have to find out for themselves which categories seems to best suit them when it comes time to deal with quitting.

We will pass up the opportunity to examine the genetic research in detail. Suffice to say that while marijuana addiction probably has a genetic component like other addictions, genetic studies have not identified any gene variants as strong candidates thus far. The case is stronger for cigarettes, but to date no genetic mechanisms have been uncovered that definitively show a neurobiological pathway that directly connects the two addictions.

There are all sorts of environmental factors too, of course. Peer influences are often cited, but those influences often seem tautological: Drug-using teens are members of the drug-using teens group. Tobacco users report earlier opportunities to use cannabis, which might have an effect, if anybody knew how and why it happens.

Further complicating matters is the fact that withdrawal from nicotine and withdrawal from marijuana share a number of similarities. The researchers state that "similar withdrawal syndromes, with many symptoms in common, may have important treatment implications." As the authors sum it up, cannabis withdrawal consists of "anger, aggression or irritability, nervousness or anxiety, sleep difficulties, decreased appetite or weight loss, psychomotor agitation or restlessness, depressed mood, and less commonly, physical symptoms such as stomach pain and shakes/tremors." Others complain of night sweats and temperature sensitivity.

And the symptoms of nicotine withdrawal? In essence, the same. The difference, say the authors, is that cannabis withdrawal tends to produce more irritability and decreased appetite, while tobacco withdrawal brings on an appetite increase and more immediate, sustained craving. Otherwise, the similarities far outnumber the differences.

None of this, however, has been reflected in the structure of treatment programs:
"Emerging evidence suggests that dual abstinence may predict better cessation outcomes, yet empirically researched treatments tailored for co-occurring use are lacking."
The truth is, we don't really know for certain why many smokers prefer to consume tobacco and marijuana in combination. But we do know several reasons why it's not a good idea. Many of the health-related harms are similar, and presumably cumulative: chronic bronchitis, wheezing, morning sputum, coughing—smokers know the drill. Another study cited by the authors found that dual smokers reported smoking as many cigarettes as those who only smoked tobacco.

All of this can lead to "considerable elevation in odds of respiratory distress indicators and reduced lung functioning in those who used both." However, there is no strong link at present between marijuana smoking and lung cancer.
Some researchers believe that receptor cross-talk allows cannabis to modify receptors for nicotine, or vice versa. Genes involved in drug metabolism might somehow predispose a subset of addicts to prefer smoking. But at present, there are no solid genetic or environmental influences consistent enough to account for a specific linkage between marijuana addiction and nicotine addiction, or a specific genetic proclivity for smoking as a means of drug administration.