A study of cannabis cigarettes for neuropathic pain
Researchers from the University of California, Davis Medical Center in Sacramento tell us “Despite [a] lack of scientific validation, many patients routinely use ‘medical marijuana,’ and in many cases this use is for pain related to nerve injury.”
In this study, “no effect on evoked pain was seen.”
First, the details.
- 38 patients with central and peripheral neuropathic pain were assigned to smoking high-dose (7%), low-dose (3.5%), and placebo cannabis.
- In addition to a change in pain intensity (the primary oucome), other outcomes included evoked pain using heat-pain threshold, sensitivity to light touch, psychoactive side effects, and neuropsychological performance.
- Neither the patients nor the researches knew their treatment (double blinded).
And, the results.
- No effect on evoked pain was seen.
- No change in pain intensity as a stand-alone outcome was reported.
- However, a mixed linear model (a statistical tool that combines several variables) demonstrated an analgesic response to smoking cannabis.
Huh?
- Psychoactive effects were minimal and well-tolerated, with some acute cognitive effects, particularly with memory, at higher doses.
The bottom line?
Despite what you might read on pot-friendly websites and in the mainstream media, the take-away point is that there was no change in pain intensity (the primary endpoint) and “no effect on evoked pain.”
The mixed linear model is a needlessly complicated statistical tool for this type of study that was probably used by the authors to find something positive about marijuana in order to get the study published. Studies of opioids don’t rely on this method. They simply use a visual analogue scale to detect analgesia.
Can we say data dredging?
Excuse me, but I can’t help thinking that the proximity of the medical center to San Francisco (about 1.5 hours) influenced their choice of statistical analysis.
6/26/08 21:43 JR
