For example, one study published in the journalÂ Neurology in 2007Â looked at the effect of smoked cannabis on HIV-associated sensory neuropathy, a potentially painful condition affecting nerves in the hands, feet, and other parts of the body. Fifty patients were randomly assigned to either smoke cannabis or placebo cigarettes that looked identical, and were evaluated based on self-reported measures of daily and chronic pain.
After five days, the smoked cannabis reduced daily pain by 34 percent, while placebo only reduced it 17 percent. The very first cannabis cigarette smoked reduced chronic pain substantially, while the first placebo had very little effect. The study also found no serious adverse events were reported during the trial.
A second study, published in 2008 in Neuropsychopharmacology, also found benefit with smoked cannabis for the same medical condition. In this case, 28 patients completed two separate five-day treatment periods, separated by a two-week washout period; in one, they smoked cannabis cigarettes four times daily for five days, and in the other they smoked placebo cigarettes. Pain was evaluated using the Descriptor Differential Scale, which allows patients to use certain words to describe pain intensity; researchers use those descriptions to assign a pain score. The study found that 46 percent of cannabis smokers achieved at least a 30 percent reduction in pain, compared to only 18 percent of placebo smokers.
The side effects again were mostly mild, two patients did experience â€œtreatment-limitingâ€ toxicities. These included one episode of â€œcannabis-induced psychosisâ€ and one intractable smoking-related cough during cannabis treatment. The symptoms resolved when the treatment was stopped. The authors noted an important point regarding smoked marijuana: â€œSmoking is not an optimal delivery system. Long-term use of smoked cannabis is associated with symptoms suggestive of obstructive lung disease, and although short-term use is not, many individuals cannot tolerate smoking.â€
The beneficial effects of smoked marijuana are not limited to only HIV-associated neuropathy. Another study, published in 2012 in the Canadian Medical Association Journal, looked into its use to control spasticity in 30 patients with multiple sclerosis. This study again had patients experience both actual cannabis cigarettes and a placebo, and it again found more benefit with the cannabis.
In this study, patients had much greater reductions in spasticity with the drug than without it; this was measured using something called the modified Ashworth scale, which is a well-validated tool assigning point values based on muscle tone, range of motion, and other factors. Pain also diminished more, based on the Visual Analog Scale, with cannabis. There were no serious adverse events reported.
Obviously, these studies do not represent a particularly large body of evidence for smoked cannabis. In fact, theÂ JAMA review concluded:Â â€œFurther studies evaluating cannabis itself are also required because there is very little evidence on the effects and AEs  of cannabis.â€