Banner
    Brain Imaging Shows Cannabis Only Brings Subjective Pain Relief
    By News Staff | December 21st 2012 11:10 AM | 5 comments | Print | E-mail | Track Comments

    Brain imaging shows us what is happening during events and stimuli but it can't tell us much about how or why. Regardless, conclusion are often drawn and the poles of cultural debates are always jumping on the latest study to affirm their beliefs.

    No one will be satisfied with a new University of Oxford study which concluded that the pain relief offered by cannabis is all subjective. The researchers found that an oral tablet of THC, the psychoactive ingredient in cannabis, tended to make the experience of pain more bearable, rather than actually reduce the intensity of the pain. MRI brain imaging showed reduced activity in key areas of the brain that substantiated the pain relief the study participants experienced. 


    But there isn't much to conclude from it.

    "Cannabis does not seem to act like a conventional pain medicine. Some people respond really well, others not at all, or even poorly. Brain imaging shows little reduction in the brain regions that code for the sensation of pain, which is what we tend to see with drugs like opiates. Instead cannabis appears to mainly affect the emotional reaction to pain in a highly variable way,"   says Dr Michael Lee of Oxford University's Centre for Functional Magnetic Resonance Imaging of the Brain (FMRIB). "Our small-scale study, in a controlled setting, involved 12 healthy men and only one of many compounds that can be derived from cannabis. That's quite different from doing a study with patients. My view is the findings are of interest scientifically but it remains to see how they impact the debate about use of cannabis-based medicines. Understanding cannabis' effects on clinical outcomes, or the quality of life of those suffering chronic pain, would need research in patients over long time periods."

    Long-term pain, often without clear cause, is clearly a complex (and expensive) healthcare problem. Different approaches include medications, physiotherapy and other forms of physical therapy, and psychological support. For a few patients, cannabis or cannabis-based medications remain effective when other drugs have failed to control pain, while others report very little effect of the drug on their pain but experience side-effects.

    "We know little about cannabis and what aspects of pain it affects, or which people might see benefits over the side-effects or potential harms in the long term. We carried out this study to try and get at what is happening when someone experiences pain relief using cannabis," said Lee.

    The Oxford research team carried out a series of MRI scans with each of the 12 volunteers at the FMRIB centre in Oxford. Before a scan, participants were given either a 15 mg tablet of THC or a placebo. THC, or delta-9-tetrahydrocannabinol, is the active psychotropic compound in cannabis – the ingredient that's responsible for the high that drives recreational use of the drug.

    To induce a certain level of pain, the volunteers also had a cream rubbed into the skin of one leg. This was either a dummy cream or a cream that contained 1% capsaicin, the ingredient of chillis that causes a hot, burning and painful sensation.

    Each participant had four MRI tests to cover each combination of THC or placebo, and chilli pain-inducing cream or dummy cream.

    "The participants were asked to report the intensity and unpleasantness of the pain: how much it burned and how much it bothered them," notes Dr Lee. "We found that with THC, on average people didn't report any change in the burn, but the pain bothered them less."

    While this average effect was statistically significant, there was great variability among the participants in THC's effect on the pain they experienced. Only six out of the 12 reported a clear change in how much the pain bothered them, for example.

    The brain imaging results substantiate the reports of the participants. The change in unpleasantness of pain was matched with a suppression of activity in the part of the brain called the anterior mid-cingulate cortex. This structure sits in a deep part of the brain and is involved in many functions, and has previously been implicated in the emotional aspects of pain. There were also changes in activity of the right amygdala that correlated with the lessening in the unpleasantness of the pain with THC. It is already known that the right side of the amygdala can be 'primed' by pain.

    Of most interest to the researchers, however, was the strength of the connection in individuals between their right amydala and a part of the cortex called the primary sensorimotor area. The strength of this connection in individual participants correlated well with THC's different effects on the pain that that volunteer experienced.


    Published in the journal Pain.


    Comments

    * AS A PAIN KILLER

    The understanding the mechanism of cannabinoid-induced analgesia has been increased through the study of cannabinoid receptors (endocannabinoids), and synthetic agonists and antagonists. The CB1 receptor is found in both the central nervous system (CNS) and in peripheral nerve terminals. Similar to opioid receptors, increased levels of the CB1 receptor are found in sections of the brain that regulate nociceptive processing.
    The following text is taken directly from the US government's National Cancer Institute website: http://www.cancer.gov/cancertopics/pdq/cam/cannabis/healthprofessional/p...

    CB2 receptors, located predominantly in peripheral tissue, exist at very low levels in the CNS. With the development of receptor-specific antagonists, much additional information about the roles of the receptors and the endogenous cannabinoids in the modulation of pain has also been obtained.

    Cannabinoids may also contribute to pain modulation through an anti-inflammatory mechanism; a CB2 effect with cannabinoids acting on mast cell receptors to attenuate the release of inflammatory agents, such as histamine and serotonin, and on keratinocytes to enhance the release of analgesic opioids.

    Hank
    Does CB2 have a sex component?  It seems strange that over 50% of people who have prescription level pain are women but only 20+% of medical marijuana cardholders are.  I mean, since it works so well for pain and all, you think women would have equal numbers there.
    Gerhard Adam
    Brain Imaging Shows Cannabis Only Brings Subjective Pain Relief
    Is there another kind of pain?
    Mundus vult decipi
    vongehr
    Exact same thought here.  Bunch of unscientific nonsense all these pot studies lately advertized on f'n "real clear science" and this conservative one here.  All the more reason to spark up a blunt for some more "subjective" results.
    Pain management with cannabis requires the right dosage. Using marijuana edibles is the right way to maintain pain reduction. This book has great recipes for edible marijuana that are easy, small and cheap to make: MARIJUANA - Guide to Buying, Growing, Harvesting, and Making Medical Marijuana Oil and Delicious Candies to Treat Pain and Ailments by Mary Bendis, Second Edition. Learn to make marijuana oil, delicious Cannabis Chocolates, and tasty Dragon Teeth Mints. goo.gl/iYjPn goo.gl/Jfs61