Chronic Pain — 20 December 2012

By Pat Anson, Editor

Medical marijuana helps make pain more tolerable, but it does not reduce the intensity of pain, according to a small study at the University of Oxford.

Researchers studied the brain scans of a dozen men given an oral tablet of THC, the psychoactive ingredient in cannabis, and found reduced activity in key areas of the brain that substantiated their pain relief.

“We have revealed new information about the neural basis of cannabis-induced pain relief,’ said Dr. Michael Lee of Oxford University’s Centre for Functional Magnetic Resonance Imaging of the Brain. “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.”

cannabissativaLee and his colleagues carried out a series of magnetic resonance imaging (MRI) scans on 12 healthy men. Before each scan, the men were given either a 15mg tablet of THC or a placebo. THC, or delta-9-tetrahydrocannabinol, is the active compound in marijuana – the ingredient that’s responsible for the “high” that drives recreational use of the drug.

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

The men were asked to report the intensity of their pain, how much it burned and how much it bothered them.

“We found that with THC, on average people didn’t report any change in the burn, but the pain bothered them less,” said Lee, who notes there was great variability in the men’s reactions. Only six out of the 12 reported a clear change in how much the pain bothered them.

The MRI scans substantiated the men’s reactions. Changes in the unpleasantness of pain were 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 has been linked to the emotional aspects of pain. There were also changes in the right amygdala of the brain, which can be “primed” by chronic pain.

Of most interest to the researchers, was the strength of the connection between the right amydala and a part of the cortex called the primary sensorimotor. The strength of the connection correlated with the effects that THC had on the men’s pain. This suggests there might be a way to predict who would see benefits from taking cannabis for pain relief.

“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,” Lee said.

“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.”

Lee adds that any kind of pain relief, whether emotional or physical, has value.

“It is impossible to recommend one single treatment, especially when there are so few therapies for intractable pain. It needs a combined approach that can involve painkillers, exercise and physiotherapy, counseling, even surgery,” said Lee.

“Living with chronic pain involves more than just coping with the pain. It runs through your life, through your decisions and what you’re motivated to do. Some people might have a known cause for the pain – MS, cancer or an injury – but many others may have no specific cause or diagnosis for their lower back or neck pain, abdominal pain, headaches or other symptoms. That can be very difficult to accept and it can be difficult to treat.”

Lee’s findings are reported in the journal Pain. The study was funded by the UK Medical Research Council and the National Institute for Health Research. Women were not included in the study because their menstrual cycles may have influenced levels of pain over the course of the 4–6 week study.


About Author

Pat Anson, Editor

Pat is Editor in Chief of American News Report. He is a veteran journalist and a former correspondent and producer for HealthWeek (PBS), Nightly Business Report (PBS) and other nationally syndicated shows. Pat has won numerous journalism awards, including a Golden Mike award for investigative reporting.

(3) Readers Comments

  1. Gustavo – I totally agree with what you are saying. In my relation with the product Marinol, it does not work that well with pain but does help with the cravings for food aka “the munchies”.

    I feel to have been a “good” study they should have had another group that was given the whole marijuana to smoke and compared it to the drugs that they have synthesized. The actual non adulterated plant form should have been used because there is no way to really know if when they synthesize a “Natural Herb” that they are getting it correct and there is also the possibility that it is a combination of the ingredients. There seems to be an underling concern on the getting “high” aspect of the marijuana. However; most of the effective pain medications on the market do or can produce a “high” to the patient.
    Looking at the broad picture, marijuana does help with pain in certain people, the same as with the pain medications some things work for 1 person and something else works for another. The reason we have so many different types of medication is that not everything works for everyone – There is no 1 shot answer. However; I am yet to hear of someone overdosing on marijuana or abusing it to the degree of resulting in death.
    The powers that be created a conspiracy against marijuana way back because they knew of its properties and of their inability to totally control it. People are finally taking the blinders off and beginning to realize that it has alot of good to offer, Besides it being 100% usable and renewable resource. It is an environmentally “Green” product.

  2. I see, so that is how it works. It affects more on the emotional side of a person that can control the pain and not relieve it according to other articles I have read. This is good because in some countries, marijuana is regarded as a bad plant that has addictive properties which is therefore illegal. At least they have found out a good use for this intriguing plant.

  3. What about CBD?? There is no mention of CBD in this article yet CBD is the cannabinoid in Marijuana known to have the pain relieving qualities.
    “”CBD (Cannabidiol). It is one of approximately 70 Cannabinoids, the most well known being THC. CBD is an amazing compound, it can be used to treat chronic pain, anxiety and other mood disorders, as well as being a neuro-protectant and a very promising anti-cancer drug. CBD’s value in treating chronic pain is enhanced over THC because it is non-psychoactive.
    CBD works against pain primarily in the peripheral nervous system. It does not work like typical pain meds by effecting the central nervous system; it works at the neuro-synapse. When we sustain injuries, often the pain is acute and disappears completely. Other times we have persistent or intermittent pain, however, with many disorders the pain is either part of the underlying problem itself (Multiple Sclerosis, Rheumatoid Disease, etc ) or the pain becomes a syndrome of it’s own. In other words, the pain takes on a life of it’s own and is now crippling the patient. “” –

    Most medical marijuana patients will tell you the T.H.C pill doesn’t quite work as well as the entire range of cannabinoids that the plant itself can offer. Still more research is needed but clarity in regards to the uses of marijuana for pain relief is becoming more apparent. In Israel they created a Marijuana strain that has mostly CBD in it so it doesn’t get you “high”, it only gives you the therapeutic effects.